A hardware device designed to take incoming packets, analyze the packets, moving the packets to another network, converting the packets to another network interface, dropping the packets, directing packets to the appropriate locations, and performing any other number of other actions. The picture shows the Linksys BEFSR11 router and is what most home routers resemble.
A router has a lot more capabilities than other network devices such as a hub or a switch that 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. Routers however can analyze the data being sent over a network, change how it is packaged and send it to another network or over a different network. For example, routers are commonly used in home networks to share a single Internet connection with multiple computers.
In the above example of a home network there are two different examples of a router, the router and the wireless router. As can be seen in the example the router is what allows all the computers and other network devices access the Internet. Below are some additional examples of different types of routers used in a large network.
Short for Bridge Router, a "brouter" is a networking device that serves as both a bridge and a router.
A core router is a router in a computer network that routes data within a network, but not between networks.
An edge Router is a router in a computer network that routes data between one or more networks.
A Virtual Router is a backup router used in a VRRP setup.
See the access point definition for further information.