Unfortunately the term "tablet" has been bastardized to mean a lot of different things at this point.
The ASUS EP121 is a full computer.
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Cintiq vs ASUS EP121Cute Advertisement.
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To bore you with a little history, for the past several years many different people have been making "tablet PC's", with the tablet (also referred to as the "digitizer") built into the screen. The actual technology of the digitizer varied, and was basically broken down into those with a Wacom digitizer and everything without a Wacom digitizer. The reason that mattered is because only wacom digitizers have pressure sensitivity. It makes a big difference for artists, and also makes "inking" (handwriting notes) more pleasant.
Tablet PC's were a niche market, and were only available as Windows systems. They came in a "slate" form (no keyboard) or a convertible form (looks like a laptop, but the screen can swivel around and lay flat over the keyboard). Convertibles were more popular, as you might imagine!
Enter the iPad. *dun-dun-dun* It was essentially a gimpy tablet pc, BUT it was small, could use the same apps as your iPod, and had the marketing power of Apple behind it.
Suddenly all the computer makers were rushing to make iPad clones. All slates. All physically small. All with wimpy processors and cellphone-based operating systems* and touchscreen digitizers with no pressure sensitivity.
This new generation of iPad-inspired systems are what people have started to call "tablets".
(*HP tried making a tablet with Windows 7, but since it had a weak processor, it was a bit silly. And it was still useless for artists, since it had no pressure sensitivity.)
ASUS is somewhat in that category, BUT it is bigger, is the only one with a wacom digitizer, it has a full-powered operating system, and it has a powerful processor. So it's really a Tablet PC, but it's trying to hide itself as one of the 'New Cool Tablets". Sort of a wolf in sheep's clothing.
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So did that explain anything, or are you even more confused now?