I always struggle with an answer but usually get something out about taking 12 to 36 hours finding checkpoints hidden in the woods using a map and compass while you run, bike, or canoe. The harder question that I never seem to successfully answer is "Why do you do it?".
This video I ran across today explains it better than I ever could.
WILD RACERS :: WHAT IS ADVENTURE RACING? from NothinButShorts International on Vimeo.