Im new to the DS world, i just got it yesterday...im an xbox 360 player...anyways...what are some good games to play online in the internet or multiplayer (i dont know what its called , its when you have a bunch of friends in the same room and play together, dont think wrong) .. also what are some good RPG games too, doesnt have to be online...i play pokemon soulsilver, and i heard sentinels of the starry skies are good too..thanks

also what is an r4 card, SD card, tt something card ? and where can i get them