I don't know but I think he's referring to Windows Tablets.
OS = Operating System and could be one of several, Android OS, Windows OS or even Apple's OS (or iOs).
Each is a regular tablet if it meet the criteria of being a tablet device, ie. smaller than a laptop, larger than a hand held smart phone.
The possible exception might be one of the not-so-popular, Phablets, which is a hybrid device trying to be the best of both worlds.
The Chinese have a tablet that can dual boot into Android OS or Windows OS with the press of a key!
Many years ago, before computers became commonplace, each company had it's own OS, Honeywell, Tandy, Burroughs, Hewlet-Packard, IBM, Texas Instruments, etc., to name but a few. The computers then were more for the hobbyists and not the homeowner. Now they're as common as the TV or telephone and they have pretty much dissolved into the three OS's we now have, mentioned above.
It'll be interesting to see how things finally merge or turn out at least.
Man...I'm getting old!!
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