what does router do and its purpose?

A hardware device designed to take incoming
packets, analyzing the packets and then directing them to the appropriate locations, moving the packets to another network, converting the packets
to be moved across a different type of network interface, dropping the packets, or performing any other number of other types of actions.

A router has a lot more capabilities than other network
devices such as a hub or a switch which are only able to perform basic network functions. For example, a hub is often used to transfer data between
computers or network devices, but does not analyze or do anything with the data it is transferring. However, a network router may take the data being sent over a network, change how it is packaged and send it to another network or over a different type of
network. For example, routers are commonly used in home networks to share a single Internet connection with multiple computers.Below are some additional examples of different types of routers used in a large network.

Brouter= Short for Bridge Router, a "brouter" is a networking device that serves as both a bridge and a router.

Core router= A core router is a router in a computer
network that routes data within a network but not between networks.

Edge router= An edge Router is a router in a computer network that routes data between one or more networks.

Virtual router= A Virtual Router is a backup router used in a VRRP setup.

from:http://answers.yahoo.com/question/index?qid=20071122105149AAOoDR4