PC refers to any personal computer. The use of PC predates the IBM PC. After the IBM PC came out, their advertising co-opted the use of the initialism. In the early days, we explicitly referred to IBM PC's to distinguish them from all others. Gradually, the generic use of PC faded.

That is, IBM and Microsoft have succeeded in the advertising war. Nowadays even many tech people will tell you (incorrectly) that the term PC applies only IBMs. "When people hear the word PC, we want them to think only of our product (IBM)."

It's true that the IBM systems were pretty clean, but not NEAR so clean and modular as current Windows machines. And the Osborne, I think, had at least as clean a design.

As technical words become widespread, I think their meanings become diffuse, more confusing, and less useful. At first, the newer meanings are just wrong, but you get to a point where ... if the vast majority of people say the word "pig" means "a type of fowl" then, well, I guess that's what it means.

Many people use the terms net, internet, and web interchangeably. Probably this reflects their own usage, but the fact that they all mean very different things is irrelevant to them. They don't know or care about the correct meanings of the words, because it's not important to them.

All blogs are websites, but not all websites are blogs. A message "board" is not a blog. Most message boards these days are websites (or are hosted at websites), but that was not always the case, as message boards predate the web.