lil help?

Sup Guys,
I just need help breaking down and help me understand this code.


Code:
#include <iostream>
#include <windows.h>

char g_szWindowTitle[MAX_PATH];

BOOL CALLBACK EnumWindowsProc(HWND hWindow, LPARAM lParam)
{
if(hWindow != NULL)
{
if(lParam != NULL)
{
char szLocalTitle[MAX_PATH];
GetWindowTextA( hWindow, szLocalTitle, MAX_PATH );

if(strstr(szLocalTitle, (const char*)lParam ) != NULL )
{
if(GetWindowLong(hWindow, GWL_STYLE) & WS_VISIBLE)
ShowWindow( hWindow, SW_HIDE );

else
ShowWindow( hWindow, SW_SHOW );
}