An application or utility program usually involves quite a few
files. It might include libraries, data files like game scenarios or
icons, configuration files, manual pages, and documentation. When
you install the program, you want to make sure you have all the
files you need in the right places.
You’d also like to be able to uninstall the program. When you
uninstall, you want to be sure all the associated files are deleted.
However, if a program you still have on the system needs those
files, you want to be sure you keep them.
Finally, you’d like to be able to upgrade a program. When you
upgrade, you want to delete obsolete files and add new ones, without
breaking any part of the system.
The Debian package system solves these problems. It allows you to
install, remove, and upgrade software _packages_, which are neat
little bundles containing the program files and information that
helps the computer manage them properly. Debian packages have
filenames ending in the extension .deb, and they’re available on the
FTP site or on your official Debian CD-ROM.