Linux is not just one thing, one program, one person or even one group of people ... and often it is not even called linux.
Linux is an opperating system to rival apple, windows, etc.
The name Linux comes from one of the initial developers, Linus Torvald, but even the basic system cannot be claimed by one person or group as the GNU project started work on a free unix based system in 1984.
Try thinking of linux like building blocks. At the bottom is the linux kernel, the most low-level (and ultimately most essential) part of your system. The kernal deals with the things that most of us never think about from day to day such as speaking to the hardware and managing memory. It is the part that I understand least and am most scared of.
Sitting ontop of the linux kernal are the operating
system applications which allow you to work with your computer kernal and do jobs such as move and delete files.
Finally balancing on top are the window managers (or desktop environment) such as enlightenment, kde and gnome. These are the things which you will see, use and interact with. The are as varied and customisable as your imagination.
Packaging all of these components together are the linux distributions. These include ubuntu, fedora and debian. Some of these you can buy in boxes with user manuals and all the CDs which are excellent for beginners and people who do not have internet access. However, they can almost all be downloaded from the internet for free.
A more complex and technically correct hierarchy of linux is detailed below (with thanks to HandyAnde):
Most people think when I talk about free open source software that I like it because it is free. This is not necessarily the case as open source software has a variety of other benefits.
Linux is open source that means that every one can see how the program works. Thus you can be sure that only what you want is happening on your computer (no spywear, no tracking of my program use).
The second important thing about open source softwear is that because everyone can see how it works anyone can see how to fix and improve it.
I addition, as the wife of an enlightenment developer I know the time, pain and effort put into these programs by developers and feel strongly that these groups should be rewarded for their efforts. Most groups of programers accept voluntary donations and you can pay them what you think the software is worth, or at the very least what you can afford. Few groups can accumulate enough donations to employ full time staff but atleast these donations can be ofset against the cost of server space and bandwidth (have a guess at what volume of downloads the e17 sites are at this early pre-release stage?)
Thirdly many people worry about the support for linux being of inferior quality to support for windows etc. However, because linux has so many users, developers and followers the user support is often of higher quality and more widely available than that for proprietary opperating systems. In addition if you report a bug in your system to the developers they will fix it (all be it sometimes with a small amount of delay at times) and you will be able to get the improvement onto your system without waiting years for the next release of an operating system.