Virtual Humans play an important role in supporting communication between human beings through their gestures and facial expressions. We are involved in the study of Virtual Humans as communication interfaces to play such a role. Virtual Humans can be classified according to their particular roles with regard to some aspects of communication. The form and method of expression of Virtual Humans can differ greatly according to what is required, for example realism or simple representational communication. Communication efficiency and transmission efficiency should be considered to be digital data. Descriptions of function, form and syntax should be also considered.