R4 cards are memory cards developed with the intent of being used with the Nintendo DS. The Nintendo DS is a portable gaming console used to play different videogames created specifically for it. The R4 cards provide additional storage space for the games that can not be stored directly on the gaming console which memory in not rewritable. R4 cards on the other hand are rewritable and can be used again and again to store different games that are compatible with the Nintendo DS. There are plenty of R4 DS games available on the internet that could have downloaded and installed directly on to these cards. When the gamer is done with a particular game stored on the R4 card, the game can be easily deleted and a new game can be stored in its place.
R4 DS games can be used to play both homebrew games as well as commercial games developed and released for the Nintendo DS. Homebrew games refer to games that are developed by users for particular hardware, such as the Nintendo DS, which are proprietary hardware and can not be reprogrammed by the user. These are generally available as free ware on the internet. This also includes fangames which are games developed by fans to imitate a particular popular game and may or may not have characters and themes similar to their popular counterparts. Another type of R4 DS games includes the commercial games which are developed by the proprietors themselves and are compatible only with the particular hardware. These are generally sold for a nominal fee. The R4 DS cards can store both types of games as long as the games are compatible with the card.