As the title of these blog suggests the full form of GNU is GNU is Not Unix.The father of Free Software Movement Richard Stallman started the Free Software Foundation in 1983. There is an interesting description he gives as to why he started the Free Software Foundation , while working at MIT's Artificial Intelligence Laboratory in the 1970s he says they lived in an Free Software Enviroment there were lots of operating systems and other software with source codes available alongwith freedom to modify and distribute them in the community but by the 1980s things changed and free software kept disappearing and the enviroment changed to more of proprietry software which Stallman felt was ugly , morally ugly.
So Richard Stallman started the Free Software Foundation in 1983 with a goal to make it possible to use software and have freedom. For that to be practicle they needed an Operating System that was Free the only free OS at that time was PDP 10 which was obsolete in 1980s and so was many of the software that they had previously written.
So they decided to build an operating system that was UNIX like and was totally FREE. For this the GNU project was started to build the GNU operating system.The following question was asked to Richard Stallman regarding the journey of building the GNU OS (it is followed by the detailed answer given by RMS)
What was the journey to develop GNU/Linux like?
We had to start from a point that was just a little more than zero, and work our way up to freedom. There were a few free programs in 1983 when I started GNU, but those were in no way near a whole OS. There was a lot of work to do, and during the 1980s, we did it. There are hundreds of components that you need to have a UNIX-like OS, even at the most basic level. A few components we found with somebody else, who wrote them for different reasons, but were free software. But the other components we had to develop.
So I wrote some of them, and recruited people to write others, and in some cases, convinced people to develop free programs — for instance, the CSRG (Computer Systems Research Group) at Berkeley. They had written a lot of code to change UNIX, but their code was mixed in AT&T’s code, and so was proprietary. I met them in 1984 and requested them to separate their software and release it as free, which they subsequently did. I wanted to use that code in the GNU system.
By 1992, we had almost the complete GNU system, but one essential component was missing: the kernel. We started developing one in 1990. I chose an advanced design, which gave it somewhat the character of a research project, and it took six years to get a test version. Unfortunately, nobody succeeds every time. But we didn’t have to wait, because in February 1992, Linus Torvalds, who had a proprietary kernel called Linux, decided to make it free. The combination of the Linux kernel with the rest of the GNU system made a complete OS, which was basically GNU, but also contained Linux. So calling it only the Linux OS is wrong; it is the GNU/Linux OS.
So you see what we call today LINUX is actually GNU+LINUX it should be described as GNU/LINUX people are of the misconception that it was LINUS Trovalds who started it off Linus provided the Kernel to the GNU project and and GNU/LINUX came into existence being free is was constantly developed and improved upon to our present day Fedora,Debian,Android,Ubuntu,Mint and thousands of other distributions of GNU/LINUX .