Keyboards are simply a tray of switches, when a user clicks a key this creates a current like an on/off switch. There are various types of keyboards including; QWERTY, ABC and Gaming.
These keyboards are the most popular around today, there named after the first 6 keys on the keyboard (q,w,e,r,t,y). the design of these keyboards were created in the 1870's by Christopher Sholes for type writers. The keys are positioned to allow you to get to the most used letters quicker.
Abc Keyboards are very rarely used though can be found in places like learning centers or primary schools as it helps the children learn the alphabet at the same time as computer skills.
Overall the QWERT keyboard is the best solution in most cases, its re-ordered keys allow the user to very easily remember and coordinate the keys. I think the ABC keyboard is not only worse but I think it's bad, primary school children should be learnt how to use a normal QWERTY keyboard, if they learn to use a ABC one they may strugle to change to the QWERTY.