The bridges used in computer networking are not like your typical bridge. This type of bridge is a internetworking device used to help conserve the bandwidth on the network. When LANs are really starting to grow, network data traffic begins to become a little overwhelming to the available bandwidth on the network media.
One way of conserving this network traffic is to slice the network up into smaller segments. These segments are connected to a bridge. Bridges are smarter than hubs and repeaters. They also use software to help get the job done. Bridges are able to read MAC addresses, which are also known as hardware addresses that are burned onto the NIC inside every computer on the network, of each data packet the is circulated on the network segments connected on the bridge. It is by learning which MAC addresses are live on the network that the bridge is able to control traffic that is local to a particular segment and keep it from spreading to other network segments that are being serviced by another bridge.