Set theory is a fundamental branch of mathematical logic that deals with the concept of sets, which are collections of objects. It provides the foundational framework for various mathematical disciplines and is essential in defining functions, relations, and cardinality. Set theory is widely used in science, particularly in fields like computer science, statistics, and probability, to model and analyze data. Key branches of set theory include naive set theory, axiomatic set theory, and descriptive set theory. Understanding set theory is crucial for grasping more complex mathematical concepts and their applications in scientific research.