The Ds has 4 capabilities .
1. Play original DS games.
2. Play GBA game cartriges.
3. PictoChat - Chat with people , around 100 feet range ( Up to 16 people )
4. Download Play - Play VS, CO-OP games whit friends ( AD-HOC )
Sry about the games I don't know much.S
I heard that MP has some difficult controls, but it has one of the beautifulest graphics on DS.
About Mario Kart? It's pretty fun, has Wi-fi ( Like MP ) up to 4 players.