Neutrinos are elementary particles that play a crucial role in our understanding of particle physics. Initially considered massless, recent experimental evidence has revealed that neutrinos possess a small but non-zero mass. This discovery has significant implications for the Standard Model of particle physics, which originally predicted neutrinos to be massless. The measurement of neutrino mass is a key factor in understanding phenomena such as neutrino oscillations, where neutrinos change their flavor as they travel. These oscillations imply that the neutrinos have different mass states, which are fundamental for accurately modeling their behavior. Understanding neutrino mass not only refines our knowledge of fundamental particles but also contributes to broader theories, such as those involving dark matter and the evolution of the universe. This book elucidates the concepts and innovative models around prospective developments with respect to neutrino mass. Also included in this book is a detailed explanation of the various concepts and applications of neutrinos. This book is a complete source of knowledge on the present status of this important field.