Why the different flavors?

As more and more people began developing unix, the more they wanted their
own implementations. Disagreement among how things should work no doubt
lead to small groups branching off to create their own version of unix.
Rather than fighting over the design of the operating system, these 
individuals simply started their own projects. This was made possible 
because of the idea of open source code. The idea of free software that
can be modified to suit your own needs is summed up at www.gnu.org.

Many distributions run on proprietary hardware and are targeted at large
businesses. Other free distributions are aimed at the end user who is looking
for a powerful and flexible operating system.

That in mind, many people broke off previous unix projects to work on
their own distributions. Over the years, these have developed into dozens
of well known, commercial, and/or popular versions used today. Below
are many of the flavors found in today's networked world. Keep in mind
that the average user will probably be experimenting with some distribution
of Linux, BSD, or Solaris.