The main purpose of this book is to present a description of the mechanism of high-temperature superconductivity and to discuss the physics of high-temperature superconductors. After a description of the BCS model of superconductivity in metals, chapters cover cuprates and their basic properties, anomalies in tunneling spectra, nonlinear excitations in solitons, evidence for soliton-like excitations in cuprates, the mechanism of C-axis phase coherence, and the mechanism of high-Tc superconductivity. The author is affiliated with the Université Libre de Bruxelles, Belgium.