This document discusses several prominent nursing theories including Orem's Self-Care Deficit Theory, Roy's Adaptation Theory, Pender's Health Promotion Model, and the Health Belief Model. It defines key concepts of each theory such as self-care, adaptation, health, and perceived susceptibility. For example, it explains that Orem's theory focuses on nursing to support self-care when patients are limited, while Roy's theory views people as adaptive systems that interact with their environment. The theories provide frameworks for understanding health behaviors and guiding nursing practice.