Apple’s Macintosh computers are usually referred to as “Macs” for short. Windows users unfamiliar with the usual way of rendering the name often write it as if it were an acronym, in all caps: “MAC.”
But a MAC is something quite different. Every computer on a network has a Media Access Control number; so when your IT support person asks you for your “MAC address,” don’t say you don’t have one just because you use Windows. Don’t ask me how to find the MAC address for your Windows computer though; I’m a Mac user.