Well, now that you know what LINUX is we need to explore how this loose collection of software is made available to the user.
The collections are called DISTRIBUTIONS or DISTROS. Several companies offer their LINUX DISTRO and SUPPORT as a commercial product, some DISTROS are freely available for download.
I am more familiar with REDHAT LINUX, so, I will use them as an example.
RHEL - Red Hat Enterprise Linux - a commercial LINUX DISTRO with SUPPORT
FEDORA - A community supported LINUX DISTRO that can be downloaded at no cost
Fedora may be a community supported product, but, RED HAT pours a good deal of time and money into the Fedora project in the form of employee development time and debugging. In return, the community reports bugs for the product for a wide variety of software configurations and computer equipment configurations. These bug reports and user experiences help RED HAT make improvements to the RHEL product.
So, if you run a business and want your server operating system to have support, RHEL may be the product you need. If you are looking for a LINUX DISTRO that has good community support, FEDORA may be your solution.
There are many DISTROS out there, about 300 at one time. The big ones seem to be:
MANDRIVA (Mandriva) Formerly MANDRAKE
CentOS a community supported derivative of RHEL