That's really not entirely true. Also Macs are PCs.
Technically yes. As PC stands for Personal Computer, which an apple computer is.
Yes, but I didn't mean that in just a literal sense. In the past, the only thing that differentiated a Mac from a PC so to speak, was the microarchitecture it was using. Mac was powerpc, from IBM, and PCs were x86 based from Intel. They now both run just about identical hardware. Theoretically, you ought to be able to run OS X on a pc. And in fact you can, although it's technically not legal. Why? Because if you purchase Mac OS, you are only allowed to install it on an Apple system. I find that kind of funny. That Blu-ray you just bought? You can only watch it on a Sony TV, and a Sony entertainment system.
The main reason for this is of course, to make money. Apple makes their money off of their hardware.
Sorry about that, don't let this hijack the thread.