The memory is just the same for both of them, but the stack and the heap are 2 different data structures that are useful for different purposes.
Stack is a very primitive abstraction that is needed by any micro processor in order to execute instructions on a couple of operands (usually processor registers or memory addresses).
The heap is a general allocation memory area where usually you want to store data that is not bound to the stack, that is their lifetime is longer that if stored in the stack, or said another way, the data is going to be accesses by different portions of code.
