Gentoo is a source based distribution, based on Debian. It will compile and install software that you choose, according to your architecture, claiming to increase performance.
Stage 1 downloads a bootstrap, which installs (again from source) the main utilities (binutils, gcc, gettext, and glibc).
However, you can opt to install from stage 2, which has the stage 1 utilities pre-compiled but goes on to install other utilities from source (a whole lot of them!)
Stage 3 is the easiest stage to install from, installing fewer packages from source than stage 1 and 2.
A GRP (Gentoo Reference platform) is the quickest install, installing whole packages such as KDE, Gnome OpenOffice.org straight from binary.