In Python, a set is a built-in data structure that represents an unordered collection of unique elements. Unlike lists or tuples, sets do not allow duplicate values, making them ideal for scenarios where distinct items are required. Introduced in Python 2.4, sets are mutable, meaning their contents can be changed after creation. They support various mathematical operations such as union, intersection, and difference, which can be particularly useful in data analysis and manipulation. Sets can be created using the built-in set() function or by using curly braces, although the latter cannot be used for empty sets.