-They let two network segments appear as one network to connected workstations.

-Their primary function is to keep traffic for one segment away from the other segment.

populated segments a network segment that contains ends nodes,such as work stations.

unpopulated segments a network segment that does not contain end nodes, such as workstations. Unpopulated segments are also called link segments.

Although some would suggest that a switch could segment a network (and it does use the MAC address for switching) more properly a bridge would be the answer if you are speaking of segmenting a network.

Repeaters and Hubs

segment

backbone