For an overview of enterprise video, here are some descriptions from a Gartner report:
Video streaming: Non-real-time streaming broadcasts have become one of the most common and cost-effective applications of enterprise video for training, demonstrations and executive announcements.
Webcasting: Streaming of live events is less common within the enterprise, with market penetration at about 1 percent to 5 percent. It's typically used to reach a large, passive audience with an event such as a CEO's speech.
Videoconferencing: Most large organizations have some conference rooms equipped for videoconferencing, but they are often underutilized. This technology is useful for multisite events that involve a large number of participants and require high interactivity. Desktop videoconferencing can be an alternative for smaller group sessions.
Telepresence: This technology makes telecommunications as intimate as an in-person meeting. Telepresence uses multiple video screens to display participants who may be in different locations. The cost may be prohibitive for many organizations, but conference room rental services could make this technology more broadly available.
Web conferencing: This is a relatively lightweight solution for giving interactive presentations, and it can include video. About 75 percent of the market goes to hosted service providers such as WebEx (now part of Cisco), as opposed to technology that's implemented in-house.
Personal/team collaboration: As universal communications platforms and products mature, Web conferencing and desktop videoconferencing will be part of collaboration solutions that also include e-mail, instant messaging, calendar sharing and phone.
Source: The Gartner View on Enterprise Video, May 2007