Gentoo:

Gentoo Linux is a Linux distribution named after the Gentoo Penguin. Gentoo is a free operating system. It is based on either Linux or FreeBSD that can be automatically customized and optimized for just about any application or need. This is accomplished by building all tools and utilities from source code, although, for convenience, several large software packages are also available as precompiled binaries for various architectures. Gentoo achieves all this via the Portage system. Extreme configurability, performance and a top-notch user and developer community are all hallmarks of the Gentoo experience. Gentoo is also appreciated for its discussion forums and the large knowledge base they represent.

Portage:

Portage is the heart of Gentoo, and performs many key functions. For one, Portage is the software distribution system for Gentoo. To update your local “Portage tree” over the internet with the latest software for Gentoo Linux, run: emerge –sync. Your local Portage tree contains a complete collection of scripts that can be used by Portage to create and install the latest Gentoo packages. Currently, we have over 10000 packages in our Portage tree, with updates and new ones being added all the time. The command to install a package is emerge packagename, Portage also keeps your system up-to-date. Typing emerge -uD world — one command — will ensure that all the packages that you want on your system are updated automatically.

Gentoo MacOS:

Gentoo MacOS allows you to use the portage tree and emerge natively under Mac-OSX. Many packages are still masked. Gentoo for MacOS X is basically just the portage package, and the portage-tree, but installed and capable of running natively under MacOS X. By installing gentoo for MacOS X you get python (or some updates to an already existing python framework – not sure), the “emerge” binary, and the portage tree (which you should sync as soon as you install it). You naturally also get the configuration files that are needed for portage to operate. And the best part is, that it is exactly there where it is under linux, and it behaves exactly like under linux.