Linux is a tried-and-true, open-source operating system released in 1991 for computers, but its use has expanded to underpin systems for cars, phones, web servers and, more recently, networking ...

It's not based on Android, the California-based technology company's mobile operating system used in billions of smartphones around the world, nor does it build upon the Linux kernel.

The lowdown on what open-source operating systems are and why they matter.

Want a truly secure operating system kernel? The Linux Foundation is partnering with Australia's national science agency, CSIRO, to roll out the seL4 microkernel.