If we are talking of stacks I thought of stacks like functions create them: An enclosed area of memory which holds all the local datas of the function and that is deallocated after the function exits again
The stack doesn't contain any persistent variables really. It's use is for subroutines (gosub, function, etc.). Return addresses and passed variables are the only types of data (I believe) that get pushed or popped from the stack.As Strider said, I think you were referring to heaps.
All in all, something that you usually wouldn't have to worry about anyways.