Router
A Router does everything that a Bridge does but as the name implies if you have multiple pathways to get information or data from LAN 1 to LAN 2 the router will choose the pathway that is best for getting the data through quickly. Routers are used primarily when you connect into a carriers network to get data across the city metropolitan area or interstate via a wide area network or global network. When you have really large networks with many LAN's and when you have many routers in the network the routers can even work out the shortest pathway to get the data through. Bridges are a point to point device but Routers are a point to multi point device. Bridges and Routers are programmable manually or more expensive units are what is called a learning device. This means they will learn the names of computers attached to them and in the case of a router it can send out search data to find out where the other routers are and learn about the pathways attached to it automatically.