Motivation theories can be categorized as internal, external, or those that emphasize the interaction between individuals and their environment. Early philosophers like Max Weber and Sigmund Freud explored motivation from religious and psychological perspectives. Maslow's hierarchy of needs categorizes needs from lowest physiological to highest self-actualization. McGregor's Theory X assumes people need direction while Theory Y assumes they can direct themselves. Herzberg's two-factor theory separates motivators like achievement from hygiene factors like salary that prevent dissatisfaction. Expectancy theory proposes motivation depends on expectancy, instrumentality, and valence perceptions.