Assembly MASM32 push and pop - windows

Question

This is a basic win32 program that I found online. So far I get everything, but what I don't get are those two lines:
push hInstance
pop wc.hInstance
Can someone explain to me what they do and if there is another way to do whatever is done by them using another instruction.
I tried to use google and other documentation and they explained very well what the push and pop instructions do, but I can't fit my understanding of them in the context of this program.
.386
.model flat,stdcall
option casemap:none
include \masm32\include\windows.inc
include \masm32\include\user32.inc
includelib \masm32\lib\user32.lib ; calls to functions in user32.lib and kernel32.lib
include \masm32\include\kernel32.inc
includelib \masm32\lib\kernel32.lib
WinMain proto :DWORD,:DWORD,:DWORD,:DWORD
.DATA ; initialized data
ClassName db "SimpleWinClass",0 ; the name of our window class
AppName db "Our First Window",0 ; the name of our window
.DATA? ; Uninitialized data
hInstance HINSTANCE ? ; Instance handle of our program
CommandLine LPSTR ?
.CODE ; Here begins our code
start:
invoke GetModuleHandle, NULL ; get the instance handle of our program.
; Under Win32, hmodule==hinstance mov hInstance,eax
mov hInstance,eax
invoke GetCommandLine ; get the command line. You don't have to call this function IF
; your program doesn't process the command line.
mov CommandLine,eax
invoke WinMain, hInstance,NULL,CommandLine, SW_SHOWDEFAULT ; call the main function
invoke ExitProcess, eax ; quit our program. The exit code is returned in eax from WinMain.
WinMain proc hInst:HINSTANCE,hPrevInst:HINSTANCE,CmdLine:LPSTR,CmdShow:DWORD
LOCAL wc:WNDCLASSEX ; create local variables on stack
LOCAL msg:MSG
LOCAL hwnd:HWND
mov wc.cbSize,SIZEOF WNDCLASSEX ; fill values in members of wc
mov wc.style, CS_HREDRAW or CS_VREDRAW
mov wc.lpfnWndProc, OFFSET WndProc
mov wc.cbClsExtra,NULL
mov wc.cbWndExtra,NULL
push hInstance
pop wc.hInstance
mov wc.hbrBackground,COLOR_WINDOW+1
mov wc.lpszMenuName,NULL
mov wc.lpszClassName,OFFSET ClassName
invoke LoadIcon,NULL,IDI_APPLICATION
mov wc.hIcon,eax
mov wc.hIconSm,eax
invoke LoadCursor,NULL,IDC_ARROW
mov wc.hCursor,eax
invoke RegisterClassEx, addr wc ; register our window class
invoke CreateWindowEx,NULL,\
ADDR ClassName,\
ADDR AppName,\
WS_OVERLAPPEDWINDOW,\
CW_USEDEFAULT,\
CW_USEDEFAULT,\
CW_USEDEFAULT,\
CW_USEDEFAULT,\
NULL,\
NULL,\
hInst,\
NULL
mov hwnd,eax
invoke ShowWindow, hwnd,CmdShow ; display our window on desktop
invoke UpdateWindow, hwnd ; refresh the client area
.WHILE TRUE ; Enter message loop
invoke GetMessage, ADDR msg,NULL,0,0
.BREAK .IF (!eax)
invoke TranslateMessage, ADDR msg
invoke DispatchMessage, ADDR msg
.ENDW
mov eax,msg.wParam ; return exit code in eax
ret
WinMain endp
WndProc proc hWnd:HWND, uMsg:UINT, wParam:WPARAM, lParam:LPARAM
.IF uMsg==WM_DESTROY ; if the user closes our window
invoke PostQuitMessage,NULL ; quit our application
.ELSE
invoke DefWindowProc,hWnd,uMsg,wParam,lParam ; Default message processing
ret
.ENDIF
xor eax,eax
ret
WndProc endp
end start

Answer 1

It's pushing hInstance onto the stack, and then popping it into the memory location of wc.hInstance.
The programmer could have equivalently written:
mov eax, hInstance
mov wc.hInstance, eax
if they knew they didn't need to preserve EAX.