Errr.. You couldn't have searched too aweful hard. http://ndiswrapper.sourceforge.net/
is the first hit on Google. and theres also the wikipedia entry with a good description.. http://en.wikipedia.org/wiki/NdisWrapper
You have absolutley no need for ndiswrapper if you don't use wireless.
And if you do use wireless, you should do some research when buying your wireless card so you get one that has Native linux drivers available, and won't need a wrapper that allows you to use the windows drivers..