Router is a device that forwards data packets from 1 LAN or WAN to another. Based on routing tables and routing protocols, routers read the n/w address in each transmitted frame and make a decision on how to send it based on the mostexpidient route(traffic load,line costs,speed,bad lines etc).Routers work at layer 3 whereas bridges and switches work at layer 2.
Multiprotocol routers support several protocols as IP,IPX,AppleTalk and DECnet.
Router functions can also be implemented by adding routing s/w to a file server.NetWare,Operating System includes routing s/w.
In older Novell terminology,a router is a n/w layer bridge.Routers also used to be called gateways.
Brouter-is a router that can also bridge.If the brouter does not support the protocol of the packet it is using or cannot deliver the packet based on protocol information, it bridges the packet using the physical address.