In information technology, the term channel is used in a number of ways.
1) In telecommunications in general, a channel is a separate path through which signals can flow.
2) In the public switched telephone network (PSTN), a channel is one of multiple transmission paths within a single link between network points. For example, the commonly used (in North America) T-carrier system line service provides 24 64 Kbps channels for digital data transmission.
3) In radio and television, a channel is a separate incoming signal or program source that a user can select.
4) In optical fiber transmission using dense wavelength-division multiplexing (DWDM), a channel is a separate wavelength of light within a combined, multiplexed light stream.
5) On the World Wide Web, a channel is a preselected Web site that can automatically send updated information for immediate display or viewing on request. See push technology.
6) In computer and Internet marketing, a channel is a "middleman" between a product creator and the marketplace. Value-added resellers (VAR) and retail store chains are examples of channels in this context.
7) Using Internet Relay Chat, a channel is a specific chat group.
8) In IBM mainframe systems, a channel is a high bandwidth connection between a processor and other processors, workstations, printers, and storage devices within a relatively close proximity. It's also called a local connection as opposed to a remote (or telecommunication) connection.
9) In a field-effect transistor (FET), a channel is the semiconductor path on which current flows.
Related terms include: clear channel, channel extender, Fibre Channel, Fibre Channel over IP, channel associated signaling, and channel bank.