Before the IBM PC there were Home Computers, of which there were many, many brands and models, all completely different from each other. Usually a Home Computer plugged into your television set, even though you could buy a monitor if you wanted a sharper picture. I loved the Home Computers because they were all a little different from each other, each inspired by some designer's whim. That was great because it made you think when you saw something that was a new idea.
Once the standard IBM PC was introduced, the market began to do nothing but make copies of this machine. This was actually a kind of death to innovation, and at a time when small computers were still very immature. Our industry decided that all computers should be like this 'IBM thing' when we didn't really even know yet how to build computers. In most respects, today's PC is still just a faster and bigger version of that now 25 year old design. :-(
One key thing that was really great about the Home Computer was its programming language, which was almost always BASIC. Each version of BASIC was a little different, but close enough that you could sit down in front of a computer you've never seen before and start writing something right away.
Another important quality of the Home Computer was its simplicity. Most of the time you only needed a couple of hundred pages to explain how to make any computer's hardware do whatever you wanted. All the graphics and sound, keyboard, joystick, I/O ports, memory maps, etc. were completely documented. And these things were also simple enough that you didn't need a degree to understand how they worked. BASIC made this even easier because you could use the command line interpreter to interactively play with the hardware. This was really personal computing, in the truest sense of the word.
IBM PC is a misnomer.