I think you mean SD cards. It stands for Secure Digital.
digital cameras suck
XD memory cards, also known as XD picture cards, are accepted mostly by older digital cameras. These include Olympus and Fujifilm cameras manufactured before 2010.
R4 cards can be real ds cards too, but some are better then others. I can recommend the iEdge card for DS, as it's simple and stable and will run anything you need it to. I got mine from dscardworld.com
Mostly SD cards or MMC cards.
Nintendo 3DS game cards are outwardly same as DS cards, except that they are white (as opposed to the DS cards' black) and have a small tab on the side to prevent them from being inserted into other DS systems. 3DS game cards are also known to have a much higher memory storage density than DS cards, at apparently 1-8 GB to the DS's 8-512 MB.
True
No, only the DSi, and all the DS's afterwards come with cameras. The original DS and DS Lite came without.
None.
memory cards
No but the credit can expire.
The Nintendo DSi is the most recent model of DS system currently available. It is basically the same as the DS Lite, but has two cameras for taking pictures, can record and edit sound and music, is compatible with SD cards, and can download and play DSiWare from the DSi Shop.
its just a digital camera and a DS combined the DS will store the pics you take