Python modules allow code reuse and organization. A module is a Python file with a .py extension that contains functions and other objects. Modules can be imported and their contents accessed using dot notation. Modules have a __name__ variable that is set to the module name when imported but is set to "__main__" when the file is executed as a script. Packages are collections of modules organized into directories, with each directory being a package. The Python path defines locations where modules can be found during imports.