deference between channels&busses in M.B?

Answer 1

Buses are physical pathways. Channels are logical ones.

For example, a (physical) data bus may support a (logical) forward link channel and a (logical) reverse link one--the two may be separated by time: a technique called time-division duplex (TDD).

Furthermore, each of the forward and reverse channels of a TDD link may support multiple users pseudo-concurrently. Each user has a time-slotted channel: an approach called time-division multiple access (TDMA).