A keyboard layout is any specific mechanical, visual, or functional arrangement of the keys, legends, or key-meaning associations (respectively) of a computer, typewriter, or other typographic keyboard.
Mechanical layout
The placements and keys of a keyboard.
Visual layout
The arrangement of the legends (labels, markings, engravings) that appear on the keys of a keyboard.
Functional layout
The arrangement of the key-meaning associations, determined in software, of all the keys of a keyboard.