What is an -og multiplexer, -og devices multiplexing, -og demultiplexer

A multiplexer (also sometimes spelled as multiplexor) is a device that can select from several different input signals and transmit either one or more output signals. A demultiplexer is a device that can take a single signal carrying multiple payloads and divide it into several streams. Some devices can do both multiplexing and demultiplexing functions and are therefore called multiplexers/demultiplexers.