Look, if you keep asking questions, we're never going to get these crappy corn husk crafts finished.

I just watched the Good Eats episode about corn so I can answer this: Yes, popcorn, hard corn, and sweet corn are all related to each other.

All corn varieties are all the same species.

Domesticated corn can also still cross freely with the wild teosinte.

All the corn we eat is basically the same, this is referring to the original ancestor to all of them