...Thanks captain obvious. PC means "personal computer". It's become a misused term thanks to Apple's stuff-chucking marketing though.
IBM stole the "PC" back in the 80s:
Alongside "microcomputer" and "home computer", the term "personal computer" was already in use before 1981. It was used as early as 1972 to characterize Xerox PARC's Alto. However, because of the success of the IBM Personal Computer, the term PC came to mean more specifically a microcomputer compatible with IBM's PC products.
But arguing about the definitions is stupid. There are so many terms that can mean different things depending on the context. You just have to go with it.
Windows computer's tend to have better prices than a Mac with comparable specs. However, Macs make up for the extra price with much better build quality. Build quality might not be much for a desktop PC (unless you care about how it looks), but for laptops build quality is really important because you want something that doesn't fall apart. If I where to get a new Laptop, I would defiantly choose a Mac.
Mac OS X is much more stable and secure than Windows operating systems. But Windows 7 is still a very slick operating system compared to previous versions of Windows. Of course the biggest advantage of Windows is the greater software availability, especially with games. However, the Mac gaming market is growing, with companies like Valve and EA (even though most of EA's games suck) making Windows/OSX games.