Khufu, Khafre and Menkaure built those pyramids.
But were they buried in them ?
Somebody was. Khufu's tomb was robbed, but the fact of the matter is, there was a burial chamber and a sarcophagus. Khafre was, most likely buried in his pyramid, but there were lots of others buried there if not. Still a tomb. Menkaure's tomb had skeletal remains in a wooden coffin with his name on it. Since there is no next of kin, we can presume it is he.
Tombs.