Every man is a borrower and a mimic, life is theatrical and literature a quotation.
- Ralph Waldo Emerson
Instead of having actual keys you can touch, feel and push, you have a bunch of pixels on a screen. In order to allow users to interact efficiently with such a system, it needs to work perfectly, and it needs to employ a number of tricks to help users get around the inherent limitations of such an unfamiliar input mechanism.
Virtual Keyboards on iPhone and Android