(1) In communications, the term channel refers to a communications path between two computers or devices. It can refer to the physical medium (the wires) or to a set of properties that distinguishes one channel from another. For example, TV channels refer to particular frequencies at which radio waves are transmitted. IRC channels refer to specific discussions.
(2) In sales and marketing, the way in which a vendor communicates with and sells products to consumers.
(3) In a field-effect transistor, such as a MOSFE T, a channel is the semiconductor path on which current flows.
(4) For IBM PS/2 computers, a channel is the same as an expansion bus.