The study of drug-receptor interactions is pivotal in understanding the molecular mechanisms underlying drug efficacy and safety. This chapter provides a comprehensive examination of the various types of drug targets, including enzymes, ion channels, G-protein coupled receptors, tyrosine kinase receptors, intracellular receptors, nuclear receptors, and cytokine receptors, as well as transport and structural proteins, nucleic acids, carbohydrates, and lipids. It delves into the physicochemical forces such as covalent interactions, hydrogen bonds, electrostatic interactions, hydrophobic interactions, Van der Waals forces, and cation-π and π-π interactions that govern these interactions. The chapter also highlights the importance of these forces in the context of drug design and lead optimization, emphasizing the structure-activity relationship (SAR) and pharmacophore modeling. By elucidating the intricate dynamics of ligand-receptor binding, this work aims to inform the design of more effective, bioavailable, and safer therapeutic agents, with a focus on improving absorption, distribution, metabolism, excretion, and toxicity (ADMET) profiles.