Underhood question

Im trying to cflush out my entire coolant system to find out why its overheating. The water pump has been changed,thermostatehas been changed and now i took it out. My question ids, im taking the radiator out and i notice another radiator looking core behind it, well in front of it towards bumber, what is this for. It looks kind of dirty just wondering what its for.

it's for A/C i believe

its your A/C condensor