A DS Game with 2 Carts

Recently i picked up James Patterson Women's Club Games of Passon at a flea market. Big hurdle the game works.

But it left me with a question. You see the game came with what my title says 2 carts. 1 for the DS and a GBA cart. I know the DS cart works. But I am curious what is the GBA cart for? I do have an early model DS that has both slots.