Heap and stack
Stack
Stack is used for static memory allocation, for example pointer to a function or a variable. It is a temporary memory allocation, which is automatically freed when the function exits. The stack is always reserved in a LIFO (last in first out) order, the most recently reserved block is always the next block to be freed. This makes it really simple to keep track of the stack, freeing a block from the stack is nothing more than adjusting one pointer.
Heap
Heap is used for dynamic memory allocation, for example when you use new in C++ or malloc() in C. Allocation and deallocation of memory from the heap is typically more work than from the stack. Heap is a memory which is allocated at run time by the operating system. Heap memory is not automatically freed, you must free it yourself (using delete in C++ or free() in C). It is allocated at compile time.