Linux (pronounced "lih-nux", not "lie-nux") is a Unix-like operating system (OS) created by Linus Torvalds. He developed Linux because he wasn't happy with the currently available options in Unix and felt he could improve it. So he did what anybody else would do, and created his own operating system.
When Linus finished building a working version of Linux, he freely distributed the OS, which helped it gain popularity. Today, Linux is used by millions of people around the world. Many computer hobbyists (a.k.a. nerds) like the operating system because it is highly customizable. Programmers can even modify the source code and create their own unique version of the Linux operating system.
Web hosting companies often install Linux on their Web servers because Linux-based servers are cheaper to set up and maintain than Windows-based servers. Since the Linux OS is freely distributed, there are no licensing fees. This means Linux servers can host hundreds or even thousands of websites at no additional cost. Windows servers, on the other hand, often require user licenses for each website hosted on the the server.
Linux is available in several distributions. Some of the most popular distributions include Red Hat Enterprise, CentOS, Debian, openSUSE, and Ubuntu. Linux also supports several hardware platforms, including Intel, PowerPC, DEC Alpha, Sun Sparc, and Motorola. Since Linux is compatible with so many types of hardware, variations of the Linux operating system are used for several other electronic devices besides computers. Some examples include cell phones, cable boxes, and Sony's PS2 and PS3 gaming consoles.