https://medium.com/@nickxla/an-introduction-to-stack-buffer-overflows-d555cc109131

Before jumping in, let’s start by an explanation of what the stack is.

The stack is a part of a computer’s memory that stores temporary variables created by each function (including main() function) as segments. The stack is managed and optimized by the CPU quite closely. Every time a function declares a new variable, it is "pushed" onto the stack. Then every time a function exits, all of the variables pushed onto the stack by that function, are freed (that is to say, they are deleted). The following schema can help you to understand its workings.