A switched LAN has a single electronic device that sends frames among the connected devices. A hub with several ports simulates a single shared phase. However a switch runs a bridged LAN with one device per segment.
A switch is given in the diagram below.
If a hub is used to connect among devices on a LAN, then only two devices can interact at a given time. However if a switch is need, the communication between two devices will not affect the other pair of devices. They can interacte at the same time.
BRIDGING AND SWITCHING WITH OTHER TECHNOLOGIES:
Bridges, Switches and Hubs are not fixed to Ethernet logical bus topology. They are available also for other networking methods such as token ring, FDDI etc. like Token ring hub and FDDI hub.