They work similar to bridges and switches in that they filter out unnecessary network traffic and remove it from network segments.
Routers generally work at the protocol level.
Routers were devised in order to separate networks logically. Most routers can also perform bridging functions. A major feature of routers, because they can filter packets at a protocol level, is to act as a firewall. This is essentially a barrier, which prevents unwanted packets either entering or leaving designated areas of the network. Typically, an organization which connects to the Internet will install a router as the main gateway link between their network and the outside world.