When viewing a drop down Menu, application commands are aligned on the left-hand side of the menu. On the right-hand side of the drop down menu, there is sometimes a string of symbols and or letters. These are called keyboard shortcuts. Each symbol or letter in a keyboard shortcut refers to a key on the keyboard. When all the listed keys are pressed at the same time the application command is executed. In other words, pressing the right key combo is the same as clicking the item from the menu.
Mac vs PC
Both the Mac OS and Windows software offer Keyboard Shortcuts, they differ though, on how they display them. In Mac software the key symbols are shown, which will not always appear on they keyboard keys.
Example:
On Windows the key abbreviation is shown followed by a “+” (plus symbol) and then the appropriate letter.
Example:
The Symbols (For Mac OS X):
The most confusing thing about keyboard shortcuts are the symbols listed in the menu. Even a tech-savy user like myself can have trouble deciphering what keys need to be pushed. It is not necessary to remember which symbol is which, but it is good to know what possible buttons the symbol could be referring too. This will at least allow you to try different key combos if you ever need too. (For times when choosing the menu item is not an option.)
Shift: 
Control: 
Option/Alt: 
Command: 
Function/fn: 
Keypad directions: 
Example:
In most applications there is a menu labeled “Edit”. Clicking on the “Edit” menu will offer choices such as “Copy” and “Paste”. The Keyboard shortcut for Copy is “
” on Mac and “
” on Windows. Pressing this button combo will copy any selected text (and or images) to the clipboard.
Windows Keyboard Tip:
When using a Windows App, pressing the Alt (or Option) Key will Underline specific letters in the program menu or in a drop down menu. Pressing these key corresponding with the underlined letter will either open the menu or activate the menu item. In effect, Windows is underlining the appropriate letter to push for each keyboard command.
Related Links:
Keyboard Shortcuts for Windows
http://support.microsoft.com/kb/126449
Mac OS X Keyboard Shortcuts
http://support.apple.com/kb/HT1343
List of the keyboard shortcuts that are available in Windows XP
http://support.microsoft.com/kb/301583
