This is a heavily oversimplified tutorial to the Advanced Package Tool, which is somewhat of a wrapper of dpkg, the Debian package manager.
In this tutorial, I will explain the basics of how to use apt, including installing, downloading, updating, and uninstalling packages.
A package tool is generally a piece of software that automates the process of installing, updating, and removing software.
Usually, such a package tool is built as a better front-end, or wrapper, of the system’s package manager, a lower-level tool for managing the software on your machine.
The package tool generally links to package repositories, including its own, and community-made ones.
In the case of apt, it is generally quite a complicated process to get a package on their repository, so often times, developers opt to either make their own package repository, make an installation program to install the software themselves, or host a downloadable .deb file (see here) on a website.