In Python, a set is a built-in data type that represents an unordered collection of unique elements. Sets are defined using curly brackets {} or the set() constructor. They are mutable, meaning you can add or remove elements after the set has been created. However, sets cannot contain duplicate elements, which makes them particularly useful for eliminating duplicates from a list or tuple.

Sets in Python are unordered, meaning that the elements do not have a defined order, and their arrangement can change. This characteristic distinguishes sets from lists and tuples, which maintain the order of elements. Additionally, sets can only contain immutable (hashable) objects, so you cannot include mutable types like lists within a set ¹⁴⁵.

Common operations that can be performed on sets include union, intersection, and difference, which correspond to mathematical set operations. These operations make sets a powerful tool for various programming tasks ²³.