This monograph delves into the theory of time-fractional diffusion and wave equations, presenting a comprehensive exploration of recent advancements in the field. Key topics include well-posedness, regularity, and approximate controllability of Cauchy problems, as well as the existence and regularity of terminal value problems. Detailed examples illustrate the applications of these equations, demonstrating their practical relevance. The content is rooted in research conducted by the author and other experts over the past five years, offering a thorough foundation for further study. This work is an invaluable resource for researchers, graduate students, and PhD candidates in the fields of differential equations, applied analysis, and related areas.