What Exactly Is A "PC"?

Maybe I'm overthinking this but I think there needs to be a fundamental discussion on exactly what a "PC" is. I say this because when one says "PC", you automatically think "Windows". But isn't a Mac a "PC" as well? It has computer parts and people use it for personal use.

Do you think that the "Mac Vs PC" ads changed that mindframe of everyone into believing that Macs were different from other computers. Brilliant strategy if you believe it worked.

What about Tablets? Are they "PCs" or are they still stuck in the category of tablets?

I just thought it would be interesting to have this discussion. Did Apple successful change people's thinking with the "Mac Vs PC" ads or does everybody see everything as a "PC"?