The longest-lasting form of package management, used by Slackware and its descendants. Something that confuses many newcomers is the extension. All Slackware packages end in '.tgz' but not all '.tgz' files are Slackware packages. Slackware packages are essentially gzipped tar files of binaries. Ordinarily, non-Slackware gzipped tar files will have the extension '.tar.gz' but sometimes are called '.tgz' as well. Which it is should be clear, based on where you download it but, if not, executing file name_of_file.tgz (or just trying to install it) will identify it.
The RedHat Package Manager format, described at www.rpm.org. This format is used by Red Hat, SuSE, and Mandrake. You can search for recent RPMs for your system using rpmfind.
The Debian package format. This is used by Debian and Debian-based distributions, such as Knoppix.
Mechanism aiming at installing with one click an application for all distributions including all dependencies.
An installation mechanism independent from the distribution, but dependent on the programming language; only available for Perl.