I just can’t figure out those pyramids

There was this guy on TV who said that the pyramids were built to hold grain. I don’t think that’s right.

Why pyramids? All Giza Pyramids Photo by Ricardo Liberato
All Giza Pyramids Photo by Ricardo Liberato

I looked up grain elevators and stuff like that and if the pyramid was supposed to hold grain wouldn’t it have a lid on the top like a big cookie jar? And how would you get the grain out? You would have to have a door at the bottom. I looked at all the pyramid pictures I could find and I didn’t see any doors at the bottom. And how come it’s not all hollow but just full of little rooms and tunnels? I haven’t figured out what the pyramids are for. I have to think about it more.