The keyboard was initially designed for typewriters because pairs of letters that were commonly used in combination, and were next to each other, would sometimes get stuck, and so this layout aimed to separate them. Also the layout is supposed to allow the typist to alternate between hands - putting alternate letters in a word on opposite sides of the keyboard, so the typist could be hitting one letter while moving their other hand to the next letter, supposedly increasing their typing speed (although it doesn't work fantastically well in practise).

It's called a QWERTY keyboard, after the first letters in the top line, but there are other types available out there.