What is Linux? Linux is an open source (free, and its source code is openly available) operating system written by Linus Torvalds. Linus wrote the OS because the currently available operating systems didnt fit his personal needs. Linux is not alone though, there are other open source OSes out there, most noteably FreeBSD. Here are some advantages of Linux:
Linux is not alone in these aspects, however. There are other OSes, such as UNIX that have some of these features. Here is a short history of UNIX and LINUX:
UNIX was first thought of in the AT&T labs, two programmers wanted to build an OS that would allow them to play a game over a network. The result is UNIX, which was quickly claimed by AT&T, who had legal ownership of the worker's OS, because they were being paid by AT&T when they created the OS, therefore it was their intellectual property. This outraged the programmers, and so they made a free version of UNIX, which later matured into another OS, which was used by Linus Torvalds. He soon grew tired of this OS, and completely re-wrote it, resulting in LINUX. There are still variants of the origional UNIX around, most noteably SCO UNIX (Santa Cruz Operation UNIX), and the aforementioned FreeBSD. Mac OS X is based on Linux as well. Linux is pronounced many ways, but the most common form of pronunciation is "Linnucks".
So how can you get Linux? There are several distrobutions to consider, personally I recommend Red Hat Linux, Debian GNU/Linux, and Slackware Linux. If you would like to get a view of most of the free OSes, then I recomend that you visit FreeOS.org.
Before you install Linux, you should make sure that all of your hardware is fully supported, which can be accomplished by visiting your distro's site and searching for hardware compatibility. Most "controllered" hardware is supported in Linux, and there is some software-based hardware that is supported. One of the worst problems with installing Linux is lack of supported hardware. Luckily, even some of the most generic hardware is supported.
If you have any further questions about Linux, feel free to email me at cpace@hnsg.net.