(1) Also known as the 'home keys' of keys in typing it is the center row of alphabetical letter keys on a typewriter or QWERTY keyboard. The entire home (or center) row consists of A S D F G H J K L. On a QWERTY keyboard, the fingers of the left hand covers the letters ASDF while the right hand covers JKL. This position is used for speed typing and enables you to easily reach any other key. Fingers always return to the home row when not being used.
(2) ASDF is commonly used in e-mail and form 'subject' lines when you have no subject to include.