Un mondo virtuale è la simulazione 3D di un ambiente interattivo accessibile da vari utenti attraverso l'uso di un'interfaccia web.

Gli utenti interagiscono con il mondo virtuale attraverso l'uso del proprio Avatar che rappresenta la loro identità digitale. Ci sono molti e diversi mondi virtuali ma tutti sono caratterizzati da sei aspetti fondamentali:

• Condivisione dello spazio: più utenti possono interagire simultaneamente.
• Interfaccia grafica per gli utenti: dall'ispirazione del mondo reale, i mondi virtuali rappresentano spazi, più o meno realistici, utilizzando figure bidimensionali animate o ambienti più immersivi tridimensionali.
• Immediatezza: le interazioni tra utenti ed il mondo virtuale accadono in tempo reale.
• Interazione: il mondo permette agli utenti non solo di utilizzare i contentuti esistenti ma anche di modificarli, svilupparli o crearne di nuovi.
• Persistenza: l'esistenza del mondo virtuale persiste a prescindere dal tempo o dagli utenti non collegati.
• Community/Socializzazione: Il mondo virtuale permette e stimola la formazione di gruppi sociali al suo interno come accade nei team, nei club etc.

I mondi virtuali nascono con diversi scopi. Inizialmente si sono sviluppati prevalentemente come giochi di ruolo on line (MMORPG - Massive Multiplayer Online Role Playing Game), ma presto si realizzò che c'erano numerosi altri scopi per creare mondi virtuali: commerciali, educativi, sociali, politici e militari.

Lista dei più conosiuti mondi virtuali con breve descrizione presa dal loro sito web:

Active Worlds

Ad oggi, più di mezzo miliardo di oggetti sono stati creati dall'incredibile ActiveWorlds community. Alphaworld, che è il più vasto mondo virtuale 3D esistente, ha creato uno spazio che è più grande dello stato della California. In ActiveWorlds puoi chattare nei mondi virtuali, costruendo in poci minuti il tuo personale mondo virtuale, o personalizzare il tuo Avatar con centinaia di possibilità.

Blue Mars

Blue Mars è una piattaforma di mondo virtuale 3D di prima classe per fedeltà, salabilità, sicurezza e connettività. Elevati standard grafici e personalizzazione degli ambienti per utilizzi aziendali e community.

Coke Studios

Coke Studio esprime una fusione musicale di elementi esistenti e diverse influenze dalla tradizione dell'est, al moderno ovest e musica regionale. Mantenendoo viva la magia delle performance dal vivo, a partire dalembodies a musical fusion of exciting elements and diverse influences, ranging from traditional eastern, modern western and regionally inspired music. Bringing alive the magic of live recordings and performances, Coke Studio prides itself on providing a musical platform, which bridges barriers, celebrates diversity, encourages unity and instills a sense of Pakistani pride. Coke Studio is an inspired step by Coca-Cola for having created a platform where renowned as well as upcoming and less mainstream musicians from various genres can collaborate musically.

Cybertown

A private 3D VR (virtual reality) home with your own personal chat, inbox, message board and free e-mail. You can invite your friends over to hang out, chat and party - all in full 3D! The Cybertown shopping malls and Flea Markets where you can buy, sell or trade cool 3D objects for your home. A Virtual Pet for your home. Customizable bodies to use in the 3D worlds. Ongoing Role-Playing Games. Interesting Clubs with 3D Clubhouses to join or start your own. Awesome movie theaters and music concerts. The Black Sun Club where you can dance in 3D and listen to your favorite tunes. Live events and celebrity chats. The opportunity to get a virtual job, earn CityCash and become a respected citizen of a large intergalactic online community.

Dubit

Dubit is a company that creates social games, virtual worlds, and interactive cartoons that sit at the centre of your transmedia experience.

Habbo Hotel

Habbo Hotel is the largest kids virtual world. It is a 2D flashbased platforms allow kids to connect and play games while socializing. Habbo is the most known and largest phenomena in this field, in the kids sector.

IMVU

IMVU is a social game and entertainment site where millions of people meet, chat, play games and have fun. 

Mobilekids

Road safety is of prime importance to us all. Children are particularly vulnerable road users. Between the ages of six and ten years old, they are slowly but surely developing into independent road users: going to school, visiting friends in the afternoon or sport practice. For this reason, it is important to make girls and boys aware of possible dangers in an age-appropriate manner and to train them to behave cautiously in road traffic for safety reasons. MobileKids adopts a holistic approach: not only does MobileKids offer children customized material, it also helps parents to protect and prepare their children even better. Parents and educational facilities are made aware of the importance of hazard prevention and receive support in the form of comprehensive information (Magazin) and Teaching aids

Moove

Dress up your 3D avatar for online chat in your own 3D chat rooms in the virtual world. Furnish your virtual 3D rooms, decorate with your pictures - with Webcam, voice, full control. Match & meet friends for 3D chat with Romance, flirt, hugs, kisses and more... In your own home it is your free decision about virtuality and making it real. You are creating this revolutionary 3D world on your own PC - always available to you. You alone control look and access of your virtual world - keep your privacy. Decorate the rooms with interactive 3D furniture, your own pictures, paper walls, lay carpets, install mirrors, change the lighting. Dress up your 3D avatars with the unique Avatar Studio. Just click a name on the member list sorted by your interests and you are coming together instantly. Chatting, laughing, kissing, hugging, lifelike movements. Exchange files, show your own pictures, marry virtually. Use cam and voice to get to know your chat partner even better. Find friends from all over the world and fall in love - "Anything goes".

Muse

Muse combines the sensory impact of television with the interactivity and networking capabilities of the Internet. The Muse software platform allows organizations to create collaborative custom solutions that utilize rich media, 3D environments, and multi-user capabilities. Using Muse, developers can create immersive 3D environments that unite video and animation, audio, html, 3D models and much more.

Playdo – Migoland

Migoland is a virtual world for kids between the age of 7 and 12.

Second Life

The user created virtual world from Linden Lab. Probably the most known virtual world to date. It allows developers to setup custom virtual spaces with advanced functionalities community and communication.

The Manor

Come in, kickback, relax, make new friends. Chat with old friends and family. The Manor is a 2D avatar chat experience that runs on most personal computers. With users creating additional Manor sites your bound to find a Manor to your liking. The Manor provides the tools to create your own avatar chat environment. You can build your own world here, with an embeded Python interpreter in the standalone clients, and CGI support on the server you can customize the experience to your hearts content. Build games with SQL database backends, education simulations, robotic controls, your only limit is your imagination.

The Palace

A flash based 2D virtual world. A visual Chat based on 2D avatars. One of the first examples of this kind. A follow-up of the Manor project.

The Sims Online

The Sims Online was a massively multiplayer online game based uponThe Sims. Launching in North America in December 2002, the game was re-branded as EA-Land (with major enhancements) in February 2008, before all activity was shut down completely on August 1, 2008.

There

There was closed, but is about to reopen. From the There website: “We will work to re-open There as a Paid Service (fees TBD, but at least $10/month) for folks 18 or older. You will be able to use your old Avatars, and will have all of the inventory and Therebucks youhad when we closed. We don’t know the opening date yet, but we do know we’ll start with ThereIM, then the public areas, then, finally, hoods, lots, FunZones, etc. And, of course, the Developer program will be re-activated along the way.”

Toontown Disney

Kids Multiplayer online game by Disney. Users can build cartoon characters, paint them crazy colors, give them funny names, and send them on adventures!

Tower Chat

Join TowerChat and join our amazing adventure. Create your own world where you can customise the way you look and your own place to meet new friends on-line. Click the link below for the list of all tools you have at your disposal as a citizen of TowerChat. You can create your own, unique image in our graphic chat. You can furnish your own chat rooms and invite your friends for your own parties.

Traveler

Nowhere on the internet will you find a more intriguing place to chat.  Our server combines 3D worlds and full duplex voice chat, allowing you to talk with your own voice and explore fantastic worlds and experience a whole new way to communicate on the internet.

Virtual Ibiza

VirtualIbiza.com is your gateway to the coolest community on the Web. A 3D world based on the hedonistic and totally fun filled island of Ibiza. A World built in an immersive 3D environment which has the look and feel of all the coolest places on the island of Ibiza. Invite people back to your own apartment, chat, meet and make friends with people via the instant messenger and web-cams.

Virtual Magic Kingdom

Quests, magic, chat, and adventure in a magical world based on Disney's theme parks. NOTE: This game has been retired. TryVirtual Family Kingdom instead.

Voodoo Chat

Voodoo Chat is a free graphical chat community! Using web pages as a backdrop, Voodoo Chatlets you chat with old and new friends in a well-blended environment that lets you feel like you're 'in the room' without taking the emphasis away from chatting. With features like animated graphics, voice chatting, interactive games, and the ability to run your own server, Voodoo Chat offers you unparalleled versatility and a world of opportunity. Come take a closer look!

VPchat

As our guest, you can chat in rooms for all ages and interests, customize your own avatar, compete in game ladders, and play our games: Backgammon, Acey Deucy, Spades, Yahtzee, Chess, Checkers and Battleship.

VZones

Do you love meeting new and interesting people? Do you enjoy creating new meaningful relationships with people from all over the world? Then VZones is the place for you! Immerse yourself in the virtual worlds that make up VZones: Dreamscape and newHorizone. These two colorful artistically rendered 2D virtual worlds make up VZones; ranging from getaway environments like beaches, underwater and casinos, to urban environments like the cities of New York and London. When you join VZones, you transform yourself into your digital self and meet others from all over the world. Your digital self is turned into a fully customizable avatar. Once inside, you will be able to talk, gesture, walk around and explore…play games, win prizes, buy, sell and lose yourself in the virtual fun. Throughout the years, thousands of meaningful relationships have been built and forged between VZones members—with many virtual weddings as well! Members create long lasting friendships that are as real and fulfilling as those in the real world.

Whyville

Whyville is a virtual world geared for teen and pre-teen girls and boys. Whyville's millions of registered "citizens" come from all over to learn, create, and have fun together. Whyville is their world. Whyville has places to go, things to do, and of course, people to see. Whyville has its own newspaper, its own Senators, its own beach, museum, City Hall and town square, its own suburbia, and even its own economy - citizens earn "clams" by playing educational games. And much, much, much more!

Worlds.com

Worlds is the pioneering platform in 3D virtual communities and rich immersive environments. Launching in 1994, Worlds leverages its patented proprietary technology in partnership with brand leaders in specific market segments to offer members multi-user environments that have interactive Avatars, rich media graphics, text chat, voice-to-voice chat, video and e-commerce. The 3D communities allow visitors to interact with each other, teleport throughout the Worlds environment as well as participate in shared experiences. Besides partnering with existing content providers that have strong brands and an existing following, Worlds also encourages individuals to create their own virtual spaces, communities and unique Avatars with easy-to-use tools. Worlds was and remains true “social networking” well before the term became mainstream.

Yohoho! Puzzle Pirates

Every activity in Puzzle Pirates is a uniquely fun puzzle! Carpenters repairing battle damage, bilge rats pumping out the bilge, sailors catching a salty wind, gunners washing and loading the cannons, the navigator setting a course that's true... every duty from sailing to leading an armada relies on yer own puzzling skills! Whether yer goin' solo or with a crew of mateys, Puzzles Pirates is the place to show your true piratey skills