In Python, a set is an unordered collection of unique elements, making it a powerful data structure for various applications. Unlike lists or tuples, sets automatically eliminate duplicate values and do not maintain the order of elements. This characteristic makes sets particularly useful for membership testing, performing mathematical operations like union and intersection, and managing large data collections efficiently. Sets are implemented using hash tables, which enhance their performance. They can be created using the built-in set() function or by using curly braces, and they only accept immutable data types, excluding mutable objects like lists or dictionaries.