Linux originates from Unix and Unix was the leading operating system in the 1970s, 80s and 90s.
Linux fits in a movement that was started by the Free Software Foundation.
That's an organization that was created as early as in the 1970s to make software available for free.
And GNU is a part of the Free Software foundation that provides free tools for
Unix as well as open source licenses to guarantee free access to application source code.
In the 1980s already many free tools were available. The only thing that was missing was
a kernel. In 1991 Linus Storval posted a message on Usenet and in that message he
announced the development of an open source kernel to be a part of the GNU project.
From the beginning it was a joint initiative of people from all over the world who are working together on the Linux kernel software.
In 1992 the first version of the Linux kernel was released and by combining the Linux
kernel with other GNU tools, it was possible to install Linux as an actual operating system.
To make installation easy, distributions are provided.
Amongst the earliest distributions were yggdrasil and Slackware, but currently they don't play an important role anymore. Red Hat
and Ubuntu are amongst the most popular distributions now. Linux is also the founder of git. While he was
working on the Linux kernel, Linus Torvald had developed a system to work together in a more efficient way.
And the result is Git, which has become the de facto standard for developing open source software.
Millions of developers are working with Git on a daily basis and behind current software projects. In Linux there often is
a GIT project which makes it possible to download the software for free and propose contributions to the software. And that
means that the open source software behind Linux is really open to anyone who wants to contribute to it.