What is the function of toggle keys?

Toggle keys are used to switch between two input modes on a keyboard. The most common toggle key is caps lock; when pressed, users can either disable or enable the keyboard to type in uppercase letters. Other toggle keys include: insert, num lock and scroll lock.

Unlike modifier keys, toggle keys don't have to be held down while pressing other keys to enable and disable functions. Some computer manufacturers add an LED light on or near the keyboard so that users can easily know whether the keys are on or off. Users with visual impairment or who constantly press the toggle keys by mistake can enable a Windows accessibility feature that produces a sound each time a toggle key is pressed.