The NMR probe has yielded an impressive panorama of detailed data on the static and dynamic magnetic properties of high-Tc materials. It is the aim of this volume to provide a comprehensive exposition of the various facets of the technique itself and to apply those results to the task of creating straightforward physical meaning for the elements of the available data. While some aspects of the underlying theory, particularly the dynamics, remain mysterious and controversial, this book renders nearly every available measurement understandable, at least in phenomenological terms. It is hoped that going forward from such a point, deeper understanding of the physics of high-Tc can be achieved.