As can be seen in the below images, there are literally hundreds (thousands?) of Linux distributions (distros).

Anyone who wants to -- and possessing the proper gumption -- can fork (clone) a copy of most open source software, so that they can make the changes that they feel are important. This can range from fixing one problematic bug all the way to coming up with something that looks and/or acts very differently from the original.

This is a strength in four ways:

1. If you want to alter open software -- you can do so.

2. distros exist that are specialized for many purposes. There are graphics ones; HAM radio ones; distros for Writers, for Doctors, for Firemen, etc!

3. Changes made to forked distros often bubble back up to the original; strengthening ALL related distros.

4. If someone falters; there are other choices.

Distributions

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Here is more summarized way to look at this:

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Distrowatch.com is a great place for news on distros, new releases, which are hot and more.