Not to burst your bubble, but this belongs under General Romhacking. Pay attention to the topic of the subforum before you post next time.

Anyways. Sprites are graphic data: if you opened up a Pokémon Yellow ROM in the program, you'd be able to edit all the game's sprites.

...Mind you, you'd also be able to do so with a more generic tool like Tile Layer Pro or Tile Molestor. (Not in Paint, though, or even Photoshop. Game hardware uses its own special storage formats.) The advantage of a game-specific tool is that it's built with a particular game in mind, so it might have extra features that would be useful for that one game (though useless for most others).