AWD vs 4WD?

Hi All,

    Can anyone give me a functional difference between
"All Wheel Drive" and "Four Wheel Drive", other than AWD
won't ruin your drive train on a smooth road?  How will
AWD do on a dirt road with a fi****ng hole at its
end?  (I asked the service dept at my Mitsubi****
dealer and got "They are on all the time".  In other
words, they are not saying.)

Many thanks,
-T