Linux is usually stable. It is Open Source, which means that anyone can modify the source code as they see fit. It is also free. Because of it's Open Source policy, there are many flavors of Linux. The most used is Ubuntu. Linux has a market share of just over 1%. Typically, Linux works on just about anything, even old computers. The downsides are that it is less intuitive than other OSes and doesn't offer much game support.