DSware: used to download games using points that can be purchased at Walmart, Best Buy etc. Similar to Wiiware for Wii.
Picto-Chat: Used to chat and draw with other DS and DSi users via Wi-Fi
Download Play: Used to download demos from the Wii or play multi-player games with friends (ex. Mario Kart)
Camera: Use to take and edit pictures. Pictures can also be uploaded onto Facebook.
Internet Browser: Used to browse Internet, however not a very fast browser.
Sound: used to record and edit/play with voice/sound recordings.
DS game slot: Used to play DS and DSi games.