A bridge is basically a device lets you to link two networks together.
Bridges are smart enough to know which computers are on which side of the bridge, so they only allow those messages that need to get the other side to cross the bridge. This improves the performance on both sides of the bridge.
As a packet arrives at the bridge, the bridge examines the physical destination address of the packet. The bridge then decides whether or not to let the packet cross.
Bridges have a capacity to filter the data traffic.
Network bridges filtering works based on MAC addresses.
Bridges works on data link layer or layer 2 of OSI model.
Bridges are mainly used to solve the traffic amount in LAN segment or congestion problem because it divides the network segment in two parts, and if LAN segment is divided into two devices then the data of one side can not go to the other side.