explanation about push ebp and pop ebp instruction in assembly

i used stack in assembly but i didn't got idea about push ebp and pop ebp.

.intel_syntax noprefix

.include "console.i"

.text

askl:   .asciz  "Enter length: "
askb:   .asciz  "Enter breadth: "
ans:    .asciz  "Perimeter = "

_entry:

    push    ebp     # establishing stack-frame
    mov ebp, esp
    sub esp, 12

    Prompt  askl
    GetInt  [ebp-4]     # length
    Prompt  askb
    GetInt  [ebp-8]     # breadth

    mov eax, [ebp-4]    # eax = l
    add eax, [ebp-8]    # eax = l + b
    add eax, eax    # eax = 2 * (l + b)
    mov [ebp-12], eax

    Prompt  ans
    PutInt  [ebp-12]
    PutEoL

    mov esp, ebp
    pop ebp     # unwinding stack-frame
    ret

.global _entry

.end