A package is a specific piece of software and data in an archive files. It can be installed and uninstalled usually be a distribution-dependent package manager (e.g. apt-get on Raspbian or pacman on Arch Linux). This is for questions related to the use and management of packages.
The package management system handles installing, upgrading, configuring, and removing packages and resolves dependencies between packages. It maintains a consistent local package database. Installation usually involves downloading package files from software repositories.