Shift; Alt; Control; Scroll Lock, Num Lock and Caps Lock; and Print Screen are some of the special function keys that are included on a PC keyboard. Each one performs a different function on its own, while some are also used in combinations for keyboard shortcuts.
The Control key performs special functions within the system. Holding it down while selecting items allows for multiple selection at once. It is also used in combination with other keys in many keyboard shortcuts to increase the number of functions specified to a system.
When the Shift key is pressed at the same time as a letter key, an upper case version of that letter is produced. When it is pressed in combination with a number key, the special character on the same key above that number is produced.
The Alt key can be used on international keyboards to access special characters on keys where there are more than two characters. Pressing it down at the same time as a letter key will produce the character showing on the bottom right corner of that key.
Caps and Num Lock are keys that toggle different functions on the keyboard. When the Caps Lock is pressed, all letters will be produced in upper case without holding down the Shift button. When the Num Lock is pressed, the numbers on the number pad which is at the right side of the keyboard can be used.