This document provides an overview of affective science and theories of emotion. It discusses what affective science is, definitions of emotion, the etymology and various classifications of emotions throughout history. Prominent theories of emotion are explained such as the James-Lange theory, Cannon-Bard theory, Schachter-Singer two-factor theory, and Lazarus's cognitive-mediational theory. The document also covers facial coding systems, basic and expanded lists of emotions, models of emotions like Plutchik's wheel and Parrott's tree-structured theory. Emotionally focused therapy and its stages are outlined in the final sections.