An "Observer" is a person or device that watches, monitors, or records events or phenomena. In scientific contexts, observers play a crucial role in gathering data, ensuring accuracy, and providing insights into various subjects, such as astronomy, biology, or social sciences. In programming, the term "Observer" refers to a design pattern where an object, known as the subject, maintains a list of dependents, called observers, that are notified of any changes. This pattern is commonly used in software development to create responsive applications, such as those involving user interfaces or event handling.