The three Lock keys are special keys designed to change the way other keys on the keyboard behave. You press a Lock key once to activate it, and you press that Lock key again to deactivate it:
Caps Lock: Pressing this key works like holding down the Shift key, but it works only with the letter keys. (Think Caps as in capital letters.) Press Caps Lock again, and the letters return to their normal, lowercase state.
Num Lock: Pressing this key makes the numeric keypad on the right side of the keyboard produce numbers. Press this key again, and you can use the numeric keypad for moving the text cursor.
Scroll Lock: This key has no purpose in life. Some spreadsheets use it to reverse the function of the cursor keys. Scroll Lock does little else celebratory.
When a Lock key is on, a corresponding light appears on the keyboard. The light may be on the keyboard or on the key itself. That’s your clue that a lock key’s feature is turned on.