The book presents an overview on important aspects of ion irradiation of surfaces, emphasizing low impact energies. Specifically, ion penetration and implantation into solids, defect creation and amorphization of semiconductors, sputtering of elemental and multicomponent targets, and ionization processes of emitted species are discussed. It provides a synoptic view of these phenomena which are strongly interrelated by the same basic processes, but are often described separately and in diverging terminology. The book tries to bridge this gap, summarizing results from experiments, computer simulations and theoretical approaches.