Chapter 1 reviews the basic theory of CR geometry, including the Levi form, CR-holomorphic vector bundles, Kohn-Rossi cohomology, Hodge theory on CR manifolds, and a proof of the Boutet de Monvel theorem on the global embedding of CR manifolds. Chapter 2 covers singularities, including resolution of singularities and the geometric genus. Chapter 3 describes the relationship between CR invariants of strongly pseudoconvex manifolds and the invariants of interior normal isolated singularities of varieties bounded by such manifolds. Chapter 4 studies the rigidity of CR morphisms using techniques from singularity theory. The final chapter presents the Bergman function theory developed by Stephen S.-T. Yau, which is used to construct explicitly infinite-dimensional moduli spaces of certain CR manifolds.