(Reference from Apple ) It is always hard to find the shortcut when you need it especially for non-heavy Mac user like myself. Let's have it here too. A modifier key is a part of many keyboard shortcuts. A modifier key alters the way other keystrokes or mouse/trackpad clicks are interpreted by OS X. Modifier keys include: Command, Shift, Option, Control, Caps Lock, and the fn key. These keys are represented by special symbols when you see them in menus and other parts of OS X: ⌘ Command key ⌃ Control key ⌥ Option key ⇧ Shift Key ⇪ Caps Lock fn Function Key When the fn key is used with the top row of keys on your keyboard, it makes them perform a different function . For example, if a keyboard shortcut is Control-F2, you press fn-Control-Brightness on your keyboard. If you look closely at the Brightness key at the top of your keyboard, there is an F2 symbol indicating that this key works as a function key (F2 or function 2) when you hold fn on the keyboard. ...