A detailed presentation of the physics of the various hysteresis models that are currently used to explain the magnetization reversal process, including coherent and incoherent magnetization processes, micromagnetism and its application in thin films, multilayers, nanowires, particles and bulk magnets, domain wall pinning and domain wall dynamics, and Preisach modelling. Some of the faulty concepts and interpretations that still exist in the literature are rectified. Magnetic imaging techniques are reviewed, including TEM, SEM, magnetic force microscopy, and optical microscopy. Temperature, field and angular dependence of coercivity, magnetic interactions and magnetic phenomena are reviewed and their effect on magnetic hysteresis is discussed. The magnetic properties of novel materials are discussed, including nanoparticles, nanocrystalline granular solids, particulate media, thin films, and bulk magnets. Finally, present and future applications of novel materials are presented, including magnetic and magneto-optic recording media, magneto-electronics, sensors, magnetic circuit design, and novel structures created from rigid, high-energy permanent magnets.