Like the term 'ley lines', the use of the term 'earth energies' has become a bit of a misnomer these days, but it seems like we're stuck with it. The term generally refers to any energy that can be dowsed on the surface of the Earth
, although it may not necessarily originate from there. Some dowsers claim that it is possible to dowse energies emanating from the closer planets.
We don't know exactly what these subtle energies are, whether they are all aspects of the same thing or different beasts entirely. But we do know that they are affected by the sun, the moon phase, the orbital dynamics of the solar system, and probably several other factors. There is some interesting research going on in Russia and other places that might one day provide a better explanation. Look up Torsion Field Theory and Vortex Theory for more information (I would avoid the Wikipedia entries - you know how rabid sceptics keep editing those to preserve their materialist world-view).
And BobD's list is fantastic, even if some of the terms might be a little idiosyncratic (and I mean that in a nice way).