This document discusses various theories of motivation. It describes Maslow's hierarchy of needs, Alderfer's ERG theory, McClelland's learned needs theory, Herzberg's two-factor theory, equity theory, Vroom's expectancy theory, and Porter and Lawler's model. Several motivational theories are compared that identify internal factors influencing motivation or the process by which internal factors influence motivation. Key aspects of motivation theories include needs, goals, expectations of performance leading to rewards, and perceptions of fair treatment.