APT, the package and tool, uses dpkg (Debian package management system) as a backend. APT downloads the package list, keep track of all packages installed, solves dependencies and remove unnecessary packages. It also allows you to query the cache, upgrade package, manage packages from multiple repositories, etc.
Any question about the APT itself or its tools should use this tag, this include:
- apt-config: to manage APT configuration.
- apt: command-line interface of apt, available from apt 1.0 (Ubuntu 14.04). Plans to replace several utilities.
- apt-key: manage the different GPG keys for repositories
- apt-cdrom: manage CD-ROM entries
- apt-cache: query the apt cache
- apt-mark: to mark specific packages as automatically or manually installed
- apt-get: the default package handling utility
Also, should include this tag the question about editing or configuring APT itself using the files in the directory
/etc/apt, like pinning, questions about other directories that are also related to APT, and the usage of the different APT API's, calls and libraries, like python-apt.
There are other front ends for most of the functions of the tools included in the apt package, like aptitude, wajig and dselect.