Please use the Simple Questions threads for questions like this.
Also, if you would have looked around a bit, you would have found another thread, dealing with the same question.
You can not trade Pokémon with GBA games. However, if you put them in the GBA slot of your DS, you can transfer Pokémon from the cartridge into your DS game.
On the other hand, trading between two DS games is possible, either via the Nintendo WiFi connection, or the Local-WLAN of the DS'.
~closed~