A networked virtual environment is distinguished by five common features

• A shared sense of space : LU

The virtual world, a common location, real or fictional.
Must present the same characteristics to all participants.

• A shared sense of presence : the avatar

Something will represent the user into the virtual world

• A shared sense of time : T0 or Tn, with n common to all users

• A way to communicate

Gesture, typed text, voice

• A way to share

More than just a video conferencing system !
It must be possible to interact with the virtual world, and this interaction must be perceptible by other users