Keylogging, (also called Keystroke logging & Keyboard Capturing) is a form of personal invasion & hacking that falls into the greater spyware category.
Keylogging is the action of record the activity of somebody typing. Intimate meta-data gets revealed, such as passwords & private interest; and even psycho-social information can be deduced from deep key analytics such as frequencies of specific key usage & typing speeds.
While the software itself is actually legal and commonly found in corporate and organizational environments, its use without the device owner’s knowledge is a criminal offense.