Chapter 2 provides an overview of cannabinoids, bridging their chemical nature with their biological fate in the body. It begins by detailing the chemical composition of Cannabis and the structural diversity that underpins cannabinoid classification into endocannabinoids, phytocannabinoids, and synthetic analogues. Key physical and chemical properties are discussed to explain how molecular features influence stability, solubility, and biological activity. The chapter then explores how specific functional groups govern interactions with cannabinoid receptors. Finally, it examines the processes of absorption, distribution, and metabolism that determine cannabinoid bioavailability and systemic exposure. By integrating chemistry, classification, and metabolism, this chapter offers essential foundations for understanding cannabinoid function, formulation strategies, and therapeutic potential.