There are four types of propagation they are
The Ionospheric wave propagation is very important to MF/HF users and of no interest to VHF / UHF users. Whilst the space and surface wave are both ground waves that behave differently. The surfave wave follows the curvature of the earth and works directly with the earth whilst the Space wave works differently, the space wave actually works as a reflection from masts many wavelengths above the ground. No part of the wave except the reflection normally come into contact with the ground.
Ionospheric propagation works in a more clearly defined way whilst it is still not understood in its entirity, more can be found in any good Ham publication on Ionospheric Propagation.