R4 is a type of flash cart, a device that allows you to play ROMs (game files) on your Nintendo DS, including Pokemon games. They are not officially sanctioned by Nintendo and are considered a form of piracy.
Here's why you might have heard the term "R4 card":
* Older information: In the past, R4 cards were a common way to play Pokemon games on the DS. However, Nintendo has taken steps to prevent the use of flash carts, making them less effective.
* Misunderstanding: Some people might use "R4 card" as a general term for any type of flash cart, regardless of its actual brand or model.
If you're looking to play Pokemon Pearl, your best option is to purchase a legitimate copy of the game for the Nintendo DS.