Ethernet bridges connect two or more Ethernet subnetworks or “bridge” the networks. Additionally bridges will monitor Ethernet traffic on all sides of the bridge and only forwards network packets which are destined to endpoints on the other side of the bridge.
Network bridges traditionally were used to connect Ethernet subnets together retaining network traffic of each subnet local to each subnet reducing the traffic on the overall network. This allows Ethernet networks to become much larger without network traffic volumes overloading the overall network. Bridging technology is included in network switches which monitor each port for traffic and only forwards traffic destined to the target network segment. Ethernet hubs do no bridging and forwards all traffic.