Simplistically, a router is a device that takes your high speed internet and splits or "routes" it wirelessly. So, your wi-fi enabled devices (like phone or laptop) do not need to be connected.
If you have a wireless network at home, the router is your access point. It connects your laptop, PC, or BlackBerry to the internet. You home PCs and you BlackBerry need to be connected to it wirelessly. If you are using security on it, you will need to enter the security key on your BlackBerry.
Posted from my CrackBerry at wapforums.crackberry.com