Despite its fundamental importance to thermal physics, fluctuation theory is only covered briefly in most undergraduate texts. This Student's Guide bridges the gap by offering a detailed look at thermal fluctuations at a level accessible to undergraduate students in physics, engineering, and applied mathematics, and to all self-directed learners approaching the subject for the first time. It places unique emphasis on principles and methods and explicitly references the contributions of Maxwell, Boltzmann, Planck, Einstein, Langevin, and other foundational thinkers. The…