The official date given for the birth of Linux is 25 August 1991, when Linus Torvalds announced that he had created a new operating system on an online forum. In one sense Linux is obviously older in the sense that Torvalds had already spent time writing the operating system before he made that announcement. The Linux that came out of that initial project was a kernel or the central part of a computer operating system, which communicates between the software and the hardware. Torvalds' original version was extremely limited and only ran on the specific hard disk drive that he owned, although it was easy enough for the technically minded to add the details for their hard disk into the source code and recompile the system. The fact that Torvalds provided the source code placed Linux as part of the then burgeoning free software movement, indeed he cites as the central point of its success the adoption of that movement's General Protection Licence. That license was at the heart of the GNU project that was building a free operating system. They were planning on making it into a complete operating system with a kernel called Hurd. The progress of Hurd was too slow and the combination of Linux and the GNU tools became what is sometimes referred to as the GNU/Linux operating system. Linux as a server system now powers the vast majority of the world's websites and without the free software to serve up pages the web might not have grown to the size that it has today. Linux as a kernel has also found a home in other operating systems, most notably in Android, which powers more smartphones than any other software system.
Back in the pioneering days of the 1990s Linux users would joke about looking forward to world domination, which seemed unlikely in a world dominated by Microsoft Windows. Linux has already achieved world domination or more accurately world wide web domination. Linux is dominant in the world of web hosting, but Torvalds' original vision was to develop a system for his desktop, not web servers or smartphones. Linux has had very limited success in the world of the desktop, by which I mean the computers on workers' desks and that people have at home. This is primarily because computers come with either Windows or MacOS or ChromeOS (another Linux derivative) installed. Few people are like me and buy a Windows computer with the intention of wiping it to install Linux. Some users install Linux because their computer is no longer compatible with Windows 10 or most Apple software no longer runs on Power PC Macs. Others might get frustrated that Windows makes their laptop fan blow constantly and have used a live USB Linux distribution and discovered that a change of operating system to Linux will solve that problem.