What is the difference between a list, set, and dictionary?

A list is an ordered, mutable collection that can contain duplicate elements. It preserves insertion order and allows indexing and slicing. A set is an unordered collection of unique elements; it is mutable but does not maintain order and automatically removes duplicates. A dictionary (or map) stores key-value pairs; keys are unique and hashable, values can be any type. Dictionaries are unordered prior to Python 3.7, but from 3.7 onward they preserve insertion order. All three are mutable, but lists support indexing, sets support membership tests, and dictionaries support key-based lookup. Example: list = [1, 2, 3]; set = {1, 2, 3}; dict = {"a": 1, "b": 2}.