This document summarizes several motivational theories including: - Maslow's hierarchy of needs theory which categorizes needs from lowest to highest order: physiological, safety, belongingness, esteem, and self-actualization. - McGregor's Theory X and Theory Y, which propose different assumptions about how to manage individuals motivated by lower or higher order needs. - Alderfer's ERG theory which groups needs into existence, relatedness, and growth. - McClelland's needs theory which identifies the needs for achievement, power, and affiliation. The document also defines motivation and discusses internal, process, and external motivational theories.