What is WPS in regard to the internet and internet security?

Im trying to change my wireless internet connection security settings in order to allow my nintendo ds to access a wi fi connection. I read on the nintendo website that the setting should be on WEP in order for it to connect. However every time i try to change the security setting to WEP a message come up saying if i change the setting to WEP, WPS is going to become inaccessible. What does this mean and is this a good or a bad thing?