A router is a device that is used to connect your PC to a network. It can be internet, or a small office LAN. They can also be used to keep the network traffic under control. Most common way routers are setup nowadays is by being connected to a single PC while sharing Wi-Fi to other devices such as laptops, phones etc. Usually routers come already setup by your ISP and they can acquire automatic settings from your PC, but sometimes there is the need to manually input things, like passwords.
How to setup a home router: technical details
There are several things you need to know before you start attaching the router to your PC and setting it up. First, whether your router has Wi-Fi capabilities, how many LAN ports it supports as well as what kind of telephone line do you require in order for it to work. Any router should come bundled with all the necessary cables which makes the whole subject of how to setup a home router rather self-explanatory, as well as a router switch which splits your telephone line from your internet line even though they go into the same socket on the wall.