Here, you discuss anything about the Nintendo DS. Keep in mind, though, you can only discuss the DS, not the 3DS. There's a different section for that.
Here you can discuss Nintendo's most recent handheld, the 3DS. Any discussion on the regular DS goes in that section. If you make a thread about the DS in the 3DS section (or vice-versa), it will be moved to the correct section.
Here you can discuss anything about the older Nintendo Consoles. It makes it easier to have this as there wouldn't be so many sections in one category. Obviously stuff about the newer consoles goes in their own section.