In Python, a package is a collection of related modules that provide additional functionality to a program. Packages are used to organize and modularize code, making it easier to maintain and reuse. A package typically contains a hierarchy of sub-packages and modules, and can be installed using a package manager such as pip. Popular Python packages include NumPy for numerical computing, Pandas for data analysis, Matplotlib for data visualization, and TensorFlow for machine learning. Understanding how to use and work with packages is essential for writing efficient and effective Python programs.