GNU was to be a complete, Unix-compatible operating system made up of free software. GNU is a recursive acronym standing for “GNU’s Not Unix!”(“Free software” is a similar term to open-source software, although free software focuses more on “freedom.” But that’s a different controversy.)

Is it GNU Linux or GNU Linux?

Linux is the kernel, one of the essential major components of the system. The system as a whole is basically the GNU system, with Linux added. When you’re talking about this combination, please call it “GNU/Linux”.

How does GNU relate to Linux?

Linux was created by Linus Torvalds with no connection to GNU. Linux functions as an operating system kernel. When Linux was created, there were many GNU components already created but GNU lacked a kernel, so Linux was used with GNU components to create a complete operating system.