When you are telling 'Linux', do you actually mean 'Linux' or 'GNU/Linux'? May be most of the time GNU/Linux. You don't get what I am telling? But that is the fact I am talking about.
Linux is the name of the Kernel, the original version was written by Linus Torvalds. And then there came GNU foundation, aimed at promoting free software. Their plan was to make a free operating system which is unix like. They were able to develop some utilities and libraries.But what missing was a kernel, which handle the hardware resources inside OS.
Linus Torvalds had wrote an initial version of a kernel based on Minix, another unix like OS. He did this as a hobby, actually he didn't like a Minix, which he was using. So he just wanted to make a new one. The name he gave to this kernel was 'Linux'. So combining the kernel Linus had and the user space utilities GNU had, a new OS was developed.
There should be a name given to the new OS. The name that somehow became popular was 'Linux'. After some time, there came a thought among the GNU people that calling it 'Linux' will disregard the efforts made by GNU people. They tried to popularize the term 'GNU/Linux' instead of Linux. But it never became popular. May be because it is difficult to say. Anyway people continued to use the name Linux.
So now we are using the term Linux for 'Linux' and 'GNU/Linux'.