Linux is an operating system based on the older Unix operating system. Linux has become the shining star of open source development and of the most prominent. Any developer can modify the source code of Linux and redistribute it as they choose. Best of all, Linux is free.
The kernel for Linux was first released in 1991, and was made for the Intel x86 PC. It has improved greatly since then, and now many different distributions are available.
So far however, Linux has been best known for its use on servers but it is moving towards increased use on desktop PCs and mobile phones and routers.
In 2004, market research company IDC collected data that said only 2.8% of PCs ran Linux while 25% of servers did.
In 2007, Dell made a large move that made Linux more available to the casual user. They began packaging their desktop and notebook computers with Ubuntu linux.
Dell adds Ubuntu (May 21st 2007)