When an energetic ion collides with the surface of a solid, it experiences forces of interaction with atoms of the solid, which condition its trajectory. There will be a certain probability, for any ion type and energy and target atom species and geometry (i.e., crystal orientation and type), that the ion will be so deflected as to be reflected from the solid surface, while there will be another probability for the ion to penetrate beyond the surface into the solid lattice. After the ion has entered a lattice, it will collide with atoms, thereby losing energy and causing atomic displacement and defect creation and if the ion is not backscattered out of the target during its slowing down or diffuses out subsequently it will eventually be entrapped at some center in the lattice. Subsequent thermal treatment can give information on the nature of these centers by studying atom motion and release into the gas phase. It is, therefore, clear that experimental measurements of reflection, penetration, and entrapment can give information on interatomic forces and dissolution processes and defect formation and the present review summarizes available theoretical and experimental data in these fields.