Hi Killaboi. Welcome to wiipros!
Coins are converted to wii points, which are used to buy games for the virtual console and other things, like the internet browser. You need to get 2000 before you can convert them, though. Every post you make in the 4 Wii Sections of the Forum gives you a coin. Each coin is worth 1 wii point. Most games for the VC cost either 500 or 1000 wii points. I hope that helps