Debian packages

Debian OS components and most of the GNU software are available in form of packages.

A package file contains:

Software
Info (control) file
Scripts (pre/post install/remove)

Naming convention:
(package-name)_(source version)-(package-version)_(architecture).deb

For example:

tar_1.16-2_i386.deb

tar version: 1.16, package version (revision): 2, architecture: i386.

The official Debian distribution located in the Debian archive, folder main.
Contrib Packages in the archive are freely licensed by the copyright holder but depend on other software that is not free.
Non-Free Packages in the archive have some onerous license condition restricting use or redistribution of the software.
Non-US Packages can-not be exported outside of the US.

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