The stack is a region of memory that tracks active function calls. Each call creates a stack frame containing local variables, return information, and temporary state.
The heap is used for dynamically allocated data that may need to live beyond the current function. Heap allocation is useful precisely because the lifetime of this data is not tied to one stack frame, but that flexibility makes ownership and cleanup important.
A useful mental model is to think of the stack as a neatly ordered set of trays. The newest tray is removed first. The heap is more like a shared storeroom: objects can remain there while different parts of a program refer to them.
The analogy is imperfect, but it exposes the central tradeoff. Stack allocation is usually simple and predictable. Heap allocation supports flexible lifetimes, while asking the programmer or runtime to manage where objects live and when they can be released.
Learning the terms in isolation is rarely enough. Their meaning becomes clearer when each definition stays connected to function calls, object lifetimes, ownership, and the behavior of a real program.