A comprehensive and up-to-date overview of soft and hard diffraction processes in strong interaction physics. The first part covers soft hadron-hadron scattering in a complete and mature presentation. It can be used as a textbook in particle physics classes. Chapters 8-11 address graduate students as well as researchers, covering the "new diffraction" the pomeron in QCD, low-x physics, diffractive deep inelastic scattering and related processes.