Answer:
I go inside boots and outside shoes. What am I?
My teeth help me suck.
I start with āeā end with āeā. I have whole countries inside me. What am I?
No matter how little or how much you use me, you change me every month.
I shift around though always slowly. I never move more than a few inches at a time. A large movement by me can kill many people. I am huge yet unseen by humans.
Almost everyone needs it, asks for it, gives it. But almost nobody takes it.