Special relativity and general relativity are the two interrelated theories that are usually encompassed in the theory of relativity. Special relativity is applied to all physical phenomena in the absence of gravity. The law of gravitation and its relation to other forces of nature is explained by general relativity. It is applied to cosmological and astrophysical realm such as astronomy. The theory of relativity explores the concepts like spacetime as a unified entity of space and time, kinematic and gravitational time dilation, length contraction and relativity of simultaneity, etc. Relativistic effects are important practical engineering concerns. Satellite-based measurements use relativistic effects to study the motion of an Earth-bound user. This book provides comprehensive insights into the field of relativity. It aims to shed light on some of the unexplored aspects of this field. The book is appropriate for those seeking detailed information in this area.