Linux which first made appearance in 1991 as a project by Linus Torvalds has now become a very popular operating system powering many desktops, netbooks, notebooks and super computers. Yes, you heard it right, Linux powers 10 super computers in the World. Linux currently is the most popular server operating systems and has got its more plus points compared to Windows servers.
Wikipedia definition states
Linux refers to the family of Unix-like computer operating systems using the Linux kernel. Linux can be installed on a wide variety of computer hardware, ranging from mobile phones, tablet computers and video game consoles, to mainframes and supercomputers
Take a look at Linux Wiki from the Wikipedia.
Check out this video and you’ll know about history and its milestones:
Also take a look at this infographic below:
You can also visit The Linux Foundation from the link below and also know about Linux 20th anniversary celebration.