Abraham Maslow's hierarchy of needs is a psychological theory that outlines a five-tier model of human needs, often depicted as a pyramid. The levels, from the bottom to the top, are physiological needs, safety needs, love and belonging, esteem needs, and self-actualization. According to this theory, individuals must satisfy lower-level needs before they can address higher-level needs. The first level includes basic necessities like food and water, while the second level focuses on security and stability. As people fulfill these needs, they seek social connections, self-esteem, and ultimately, personal growth and fulfillment through self-actualization.