Answer-1. what is stack segment: In computing, a stack is a data structure used to store a collection of objects. Individual items can be added and stored in a stack using a push operation. A stack in which items are removed the top is considered a "LIFO" (Last In, First Out) stack.
also push and pop instruction:
The easiest and most common way to use the stack is with the dedicated "push" and "pop" instructions.
1."push" stores a constant or 64-bit register out onto the stack. The 64-bit registers are the ones like "rax" or "r8", not the 32-bit registers like "eax" or "r8d".
2."pop" retrieves the last value pushed from the stack.