tablets pcs is supposed to mean exactly, so I can only assume it's trying to say in a kind of shorthand way something about tablet personal computers, of which there are now umpteen (the Amazon Kindle Fire, for example, pictured at right), if this article in Tech Radar is anything to go by.
The i-Pad is of course the obvious example when anyone thinks about tablets - that is, when anyone else thinks about them. When I hear the word 'tablet' and 'computer' in connection with each other I think of the tablets that my colleagues at my last job used, which often seemed to be a bit of a nightmare. (The tablets, not the colleagues, that is.) If they weren't playing up in some way, they would prefer to do their own thing, often causing havoc for the user (actually that's not unlike my colleagues too - just kidding!). Yes, of course, part of it was familiarity with the machine, but part of it was also the general quirkiness of these particular versions of the computer.
One of my colleagues liked to keep her tablet screen on a very small font - I found it practically impossible to read, and don't know how she managed. Though admittedly she hadn't been wearing glasses since she was eight.
My daughter has an i-Pad, and once you get used to its systems (which are similar for the most part to the i-Phone, which my wife has had for some time) it's pretty functional. (my grandson, of course, breezes through it). I quite like the touch screen approach for some aspects of use, though I can't say that tapping out messages one finger at a time onto a screen is really progress, to my way of thinking. I suspect anyone who touchtypes on an ordinary PC would find the same thing.
I guess it's all relative. I've watched a friend of mine who's only recently got his first laptop, and it brings back all the memories of trying to stop the cursor racing all over the screen, or figuring out how to land it on precisely the right spot: things that you do as a matter of course once you've been into the computing world for some time (like about 22 years in my case, with a PC, and even longer with office computers). You also forget just how intuitive you become when getting used to a new computer or an upgrade. What in the past would have flummoxed you becomes fairly easy to figure out with two decades of experience.