This document provides an overview of nursing theory, including its domains, paradigms, and common theories. It discusses how nursing theory describes concepts like person, health, environment, and nursing. Several influential nursing theorists are mentioned, such as Nightingale, Peplau, Henderson, Rogers, and Neuman. The document also provides an example of how Levine's Conservation Theory can be applied to understand the influences on and nursing care of preterm infants in the NICU.