The MAC keyboard although similar to a standard PC keyboard, does have some Mac specific keys. These keys allow access to those special mac features. Below is a quick list of these keys, and a basic list of some common useful keyboard shortcuts.
Mac specific keys
Dashboard key, Opens up the dashboard and display any widgets that have been setup.
Expose key is a feature of the Mac OS X operating system, Expose gives the user a quick preview of all open windows.
Command key, is equivalent to the Windows key on a standard keyboard.
Options key, This key is equivalent to the ALT key on a normal keyboard.
Command-D Duplicate selected item
Command-N New Finder window
Command-M Minimize window