Most of the modern Ethernet networks use LAN switches and for the Network Admins it’s very essential to understand how this basic, yet very important component of the network operates. I came across an excellent document in cisco site about How LAN Switches Work. The document explains what a LAN switch is, how transparent bridging works, what are VLANs, trunking, and spanning trees.
Switching allows a network to maintain full-duplex Ethernet. Before switching existed, Ethernet was half duplex. Half duplex means that only one device on the network can transmit at any given time. In a fully switched network, nodes only communicate with the switch and never directly with each other. In the road analogy, half duplex is similar to the problem of a single lane, when road construction closes one lane of a two-lane road. Traffic attempts to use the same lane in both directions. Traffic that comes one way must wait until traffic from the other direction stops in order to avoid collision.