The field of cosmology investigates the origin, evolution and the future of the universe as well as the scientific principles and laws that guide these phenomena. The fields of physics and astrophysics use mathematical formulations, scientific observation and experimentation for the development of this subject. The universe is believed to have started with the big bang, after which it underwent a process of cosmic inflation. Modern cosmology evolved after the formulation of Einstein's general theory of relativity. Observations of the cosmic microwave background radiation, new galaxy redshift surveys, gravitational lensing, observations of supernovae, etc. have further advanced the understanding of the universe. This book is a valuable compilation of topics that covers the most fundamental theories and principles of cosmology. It presents the complex subject of cosmology in the most comprehensible and easy to understand language. This book is meant for students who are looking for an elaborate reference text in this domain.