system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5 - Why a Mac is called a Mac and not a PC? Other than OS, what's the defining difference? 

I've always thought PC stood for "Personal Computer". Isn't that what a Mac is? Other than OS they're exactly the same thing, with different hardware. I understand it's easier to tell the difference when discussing the two types of computers, but, what about any type of Linux system? they're called PC's also. different OS and all.

it's not that huge of a deal I guess, but it just bugs me.

EDIT: Marking. Never really dawned on me, It makes sense though. thanks.

EDIT 2: Little more than marketing, but still makes sense.
gpt
Back in the 80s and early 90s we didn't call them PCs, we called them "IBM Compatible". It used to be you had a number of different types of computers that didn't play nicely together. You had Macs, Tandies, Commadores, and IBM machines (which ran DOS).  DOS exploded and the others, including Apple's for a number of years, fell by the wayside. Around the time Windows 95 came out personal computing started to grow, perhaps as a result of that revolutionary operating system. With one primary form factor and operating system, and Mac, at this point, becoming a tiny portion of the market,  it didn't make sense to identify the bulk of computing by compatibility with a single company. At the same time, computing is becoming more user friendly and it's starting to look like *everybody* will get one eventually, it starts losing that image as a toy for geek hobbyists and starts becoming relevant to the average person. A "personal" computer helps to portray this.