In Python, a dictionary is a built-in data type that allows you to store data in key-value pairs. Each key in a dictionary is unique and immutable, meaning it cannot be changed once created. This structure enables efficient data retrieval, as you can access values quickly using their corresponding keys. Starting from Python 3.7, dictionaries maintain the order of insertion, making them more predictable. They are versatile, allowing values to be of various data types, including numbers, strings, lists, or even other dictionaries. This makes dictionaries an essential tool for organizing and managing data effectively in Python programming.