Gentoo is a source based LinuxDistribution, sometimes also called a meta-distribution. It has a system called Portage which attempts to combine the best of PackageManagement from LinuxDistributions like Debian with the power of BSD Ports. There are (almost) no binary packages, instead, everything is compiled from SourceCode. This means you have total control and lots of room to tweak your system, though it is of sometimes doubtful benefit and requires GHz-class systems to be bearable.
See also:
Part of CategoryDistribution
19 pages link to Gentoo:
lib/main.php:944: Notice: PageInfo: Cannot find action page