Technologies used in teleconferencing and videoconferencing

What is teleconferencing? What is videoconferencing? Can you differentiate the two? What are the technology being use in tele and in video conferencing?
A teleconference is a telephone meeting among two or more participants involving technology more sophisticated than a simple two-way phone connection. At its simplest, a teleconference can be an audio conference with one or both ends of the conference sharing a speakerphone.

A videoconference is a method used to allow people at remote locations to join in a conference and share information. It was originally done with analog video and satellite links; it now is performed with compressed digital video transmitted over a local area network or the Internet. A video camera and a speakerphone are connected to a PC at each site and the PCs are connected to the network or Internet.

From an application standpoint video conferencing has gone far beyond looking at a picture of a particular person. User can now update charts and create drawing on a chalkboard, all online. Desktop video and chalkboard programs such as Microsoft NetMeeting are becoming more and more popular and GroupWare applications such as Lotus Notes are helping people work together.

With considerably more equipment and special arrangements, a teleconference can be a videoconference, in which the participants can see still or motion video images of each other.