A bridge is a device that connects different network technologies which transmit the same signal.
A bridge makes decisions on what traffic should be forwarded based on the destination MAC address that is inside the Ethernet frame. This decision making is what modern day switches do.
A bridge can connect different physical networks with different topologies.
An example of a bridge is a wireless access point. A wireless access point connects a wired Ethernet network with a wireless network. The wireless access point looks at the destination MAC address and determines whether to send the traffic to the wired Ethernet network or the wireless network.
