What is Router? (What is the difference between a Router, a Switch, a Hub and a Bridge)

Router is probably the heart and soul of a computer network. It can be compared to that department of a Post Office which is responsible for classification of mail based on address. Router is pretty much like an intermediate post office. A router receives data from a node, a computer or many a times a neighboring router. It is then responsible for the following primary functions:

1. On receiving data it looks at the content which has information (source, destination, size, priority etc.) about the data. 
2. It looks up its own data base to find a the best route for the data 
3. It choses the appropriate output channel and sends data on it to the next "hop"

Hop is nothing but a jump to the next node. If someone tells you, "The maximum hop of this data is 7" it means that this data can travel across 7 nodes only after which it will cease to exist. 

This is a very primitive explanation of a router good enough for a beginner to get hold of the concept. I will deal with it in much details in the next few days. I am currently working on a technology called Optical Burst Switching and also on routers that can support this technology. As such routers is my love and would like to do justice to it :) 

Hope to have you engaged in this work!