What is this tag about?
Though the name is a quite good association, this tag only covers a part of keyboard-related issues -- that is, as long as the keyboard comes "buit-in" with your device. In most cases, this will be the "virtual" keyboard on your display, but it might also be a built-in hardware keyboard (as e.g. the motorola-droid or the htc-desire-z feature it.
Are there other tags I should consider?
Yes, there are: