Book excerpt: From the early wave-particle arguments to the mathematical theory of electromagnetism to Einstein's work on the quantization of light, different descriptions of what constitutes light have existed for over 300 years. This book examines the photon phenomenon from several perspectives. It demonstrates the importance of studying the photon as a concept belonging to a global vacuum (matter-free space). The book explains the models and physical and mathematical descriptions of light and examines the behavior of light and its interaction with matter.