Linux is  the most popular Unix variant for PCs. Originally created by Linus Torvalds,then a student at the University of Helsinki, and developed collaboratively over the Internet with the help of other programmers and developers. It is a type of operating system and Linux is a good example of an Open Source software as its source code is available free to anyone to change and develop under the GNU General Public License. 

Linux has a lot of advantages and in  many areas, ranging from  stability to speed, user friendliness to serious computing such as development and networking. Linux has long been praised for its stability, indeed a lot of the web is run on Linux boxes which have been  known to run for months or even years at a time without crashing, freezing, or even having to be rebooted!!!   

However it is its approach to computing which makes its popular.Its completely free, there are thousands of games, scientific and productivity software available to be downloaded. There are also a lot of support from commercial developers and there is a growing list of software to be  purchased.