OS X - Help With Meaning of Symbols for Keyboard Shortcuts
OS X offers keyboard based shortcuts for faster access to functions available through both the desktop and application menus.
This document offers a list of the symbols that are expressed to execute available keyboard shortcuts.
If you turn on Sticky Keys in Accessibility preferences, you see the Command, Shift, Option, and Control key symbols on your screen when you press those keys. To open Accessibility preferences, choose Apple menu > System Preferences, then click Accessibility.