Bose-Einstein condensation is a phase transition in which a fraction of particles of a boson gas condenses into the same quantum state known as the Bose-Einstein condensate (BEC). This book, a broad study of nonlinear excitations in self-defocusing nonlinear media, presents a wide array of findings in the realm of BECs and on the nonlinear Schrodinger-type models that arise therein. It summarizes state-of-the-art knowledge on the defocusing nonlinear Schrodinger-type models in a single volume and contains a wealth of resources, including over 800 references to relevant articles and monographs...