This book presents a unified description of binding equilibrium for a wide variety of systems focusing on acid-base and coordination chemistry, adsorption at interfaces, and electron binding in electrochemistry. It overviews more complex phenomena such as competitive binding to different sites and of different ligands. Multiple sites such as those occurring in macromolecules, colloidal oxides, humid substances, and proteins are briefly discussed and many experimental results for these types of systems are analyzed. Titrations and consideration of the distribution of binding constants are also presented. The book is mainly directed at undergraduate/graduate students of chemistry, biology, and earth sciences. It is supplementary to the standard physical and analytical chemistry courses and will help both students and teachers get a more in-depth knowledge and understanding of the systems analyzed.