A set is a collection of distinct objects, considered as an object in its own right. Sets can contain anything, such as numbers, letters, or even other sets. The key characteristic of a set is that it does not allow duplicate elements; each item can only appear once. Sets are often used in mathematics and computer science to group items together for various operations. In programming, sets are implemented in many languages, such as Python, Java, and JavaScript. They provide efficient ways to perform operations like union, intersection, and difference. Sets are useful for tasks that require uniqueness, such as removing duplicates from a list or checking membership efficiently.