A SHORT, SWEET, VISUAL EXPLANATION OF GEOTHERMAL
This short Flash presentation is the quickest way to get an understanding of geo priniples:
www.geoexchange.org/animation/flash-56k.html
(Courtesy of: www.geoexchange.org)

GEOTHERMAL: WHAT IT IS AND WHAT IT’S NOT
Geothermal is a tried and true, proven technology which is so widely misunderstood, that it is usually referred to as “Geothermal Energy”… but that is a misnomer.

GEOTHERMAL OR GEOEXCHANGE
Geothermal energy is the kind of energy found in the hot springs in Iceland, for example, where hot water from naturally occurring can be run through pipes in the floor for heating, for example.
A geothermal system using a ground source heat pump is the most common application in North America, and it does not rely on nature having put a hot-spring on your property. The typical system  employs a heat pump to use the Earth’s heat (or to “dump” heat if the geo system is being used for cooling).