Satoru Iwata has explained what happens when you press the Home button on your Nintendo 3DS. Yes, in a recent investors meeting, Nintendo's President showed off some the 3DS's extra features including the Game Memo, Friend List and Notification Applet.
If you select Game Memo, your game will be displayed in its paused state on the top
screen (you can either view one screen or both screens from the game on this top screen) and the Memo will appear on the Touch screen. This enables you to write notes - perhaps about a puzzle in the game - on the touch screen. Your memos can be saved to a SD card as an image.
We know that Friend Codes are back for 3DS but Nintendo has added a Friend List this time which enables you to see which of your friends is online and what they're playing. You can block your current online status if you don't want your friends to know what you're playing. You'll know when one of your friends appears online as the 3DS's LED will flash orange.
Finally, if you want to know about your latest SpotPass and StreetPass transfers, go to the Notification Applet. When you receive something new, the Applet's icon on the Home menu will change. Also the notification LED will flash when SpotPass and StreetPass transfers are made while your system is in Sleep mode.