Linux can be difficult.  You find some great software package on the
web, you download it to your Linux computer, you run it, and it crashes. 
There can be lots of reasons but, commonly, the problem is something
called "dependency hell."  Linux applications depend on one another;
they rely on shared libraries, for example.  If all this software was not 
compiled with the same Linux kernel and the same compiler, you can get
"hell."  Linux distributions like Susie and Debian work to get around 
this problem but there is a price.  Part of the price is that the newest 
software can be old by the time that they get everything working 
together and deliver the solution to you.  Another price is that the 
solutions are designed for the average user and, hence, will not be 
optimized and customized for your needs.

There is solution: download source code and compile everything on the
user's computer.  This is the Gentoo approach.  Gentoo is software and
people and a worldwide array of servers organized to make this easy. 
The core of the Gentoo software is called Portage.

Suppose you have a Gentoo-enabled computer and you want to add a
software package, a "mysql" database, for example.  You connect to the
Internet and type in the command "emerge mysql".  The Gentoo software 
on your computer then connects to one of the Gentoo servers on the
Internet, downloads the necessary software, compiles it to conform to
your specifications for your system, and installs it in appropriate
directories.  In most cases, the process is completely automatic after
the initial command.

To make this work, your local computer has to know what software
packages are available on the servers.  In the Gentoo system, this
information is called the "Portage Tree," so-called because similar
packages are grouped together into a tree of directories.  The software
packages on the servers are updated frequently; hence, you must be able
to update your Portage Tree.  The Gentoo "emerge sync" command does
this.

If the Gentoo approach is to be practical, there must a wide array of
software packages available from the Gentoo servers.  There is.  At this
writing, there are about 7000 packages in the Portage system with new
ones being added all the time.  Packages include Linux kernels, the
usual libraries, window managers like KDE, office software, web
browsers, compilers, games, audio and video players, and, of course,
updated versions of the Portage software.  Several different versions
of Linux kernels are available: some optimized for stability, some for
security,  some for speed (e.g., for games), and some for advanced
(i.e., bleeding-edge) features.  With Gentoo, you get lots of choices.

To be honest, the Gentoo approach has some disadvantages.  Compiling
software on the user's computer takes time, especially on old and slow
computers.  Storing source code takes disk space.  And, source code
takes longer to download than compiled binary code.  The issue for each
individual is whether the advantages of Gentoo outweigh the
disadvantages.

You can learn more about Gentoo by exploring this web site
(www.gentoo.org).

Incidentally, a gentoo is a kind of penguin.  But the Gentoo mascot
isn't a penguin; it's a cow.