Used with large networks to control access where cabling is shared. Analogy of a teacher calling on only students who raise their hand. When there is no MAIN host. Used on common circuit networks like polled networks. Computers wait until the circuit is free.
Ethernet is a good example - collision detection network.
Used for small networks with little access. No time is spent waiting for acknowledgement of a poll request or a token to be passed. Fast for small networks. Human and network. There are 2 categories of network errors.