What exactly does the garbage collector free: heap memory area or stack?

The garbage collector in Java frees memory in the heap area, where objects created during program execution are stored.

The stack is used for storing local variables and method calls, and memory in the stack is managed automatically when entering and exiting methods — it is freed immediately without the involvement of the garbage collector.

In summary:

• Heap: the garbage collector frees unused objects.
• Stack: memory is freed automatically when a method finishes, and the garbage collector is not needed here.