Difference between routers and gateway

can anyone tell me difference between routers and gateway.
and reference site where these topics are discussed in detail.

routers send data to a specific location based on a address for the network segment. The benefit is the ability for a router to search routing tables and find the shortest path to the destination. The downside to routers is that they are protocol dependent and therefore can only route data between network segments using the same protocol. Today this is a moot because everyone uses TCP/IP and has an open architecture. This is why, for example, data can be sent between a Windows NT network and a Netware network.

Here's how a router works: When it receives a packet and sees a MAC address (hardware address) that is not on the local segment, it strips away the MAC address, looks at the IP address (software address), searches its routing table, and then sends the packet based on the IP address to the router that's connected to the segment that contains that address.

Gateways are network points that acts as an entrance to another network. On the Internet, a node or stopping point can be either a gateway node or a host (end-point) node. Both the computers of Internet users and the computers that serve pages to users are host nodes. The computers that control traffic within your company's network or at your local Internet service provider (ISP) are gateway nodes.

In the network for an enterprise, a computer server acting as a gateway node is often also acting as a proxy server and a firewall server. A gateway is often associated with both a router, which knows where to direct a given packet of data that arrives at the gateway, and a switch, which furnishes the actual path in and out of the gateway for a given packet.

In simpler terms a router is like a elevator in the building. It can take you to any floor [distination] and back again [source]. This would work with any routable protocol [tcp/ip, ipx, decnet..]

Your first door to the elevator is your gateway. This is all your pc needs to know since the router will take it from there and make sure it gets to where you want and back again. You can access the World by going thru that first door [gateway]

In common usage the terms are the same. For example, when you define the "Default Gateway" in Windows it better be a device that either is a router or has another Default Gateway command. Eventually the chain of Default Gateways will either be a router or a device that defines the target network.