In mathematics, a set is a well-defined collection of distinct objects, considered as an object in its own right. Sets are fundamental to modern mathematics and are used to define nearly all mathematical objects. The objects in a set are called elements or members. Sets are typically denoted by curly braces, for example, \( \{a, b, c\} \), and can contain numbers, symbols, points, or even other sets. A set class, in a more advanced context, refers to a collection of sets that share a common property or structure. In set theory, set classes can be used to study properties of sets and their relationships. For example, the class of all finite sets or the class of all countable sets are set classes. Set classes are crucial in various branches of mathematics, including algebra, topology, and analysis, as they help in understanding the behavior and properties of mathematical structures. However, dealing with set classes can lead to paradoxes, such as Russell's Paradox, which arises when considering the set of all sets that do not contain themselves. This has led to the development of axiomatic set theories, like Zermelo-Fraenkel set theory, to provide a more rigorous foundation for dealing with sets and set classes.