Gnu can be used to describe the gnu project, the gnu license or the gnu coreutils. In this context, they mean that Linux by itself isn’t enough to be the a free desktop, and needs the gnu software to be the system they care about. (There can be controversies on whether gnu is needed or not, since it’s possible to create a distro without the coreutils, but let’s not get you confused right now)
I see the term gnu around but what is it?
https://www.gnu.org/ and https://www.gnu.org/distros/free-distros.html
Its a set of software tools, that are often bundled together with the Linux-Kernel. Most Distros use them.
A bunch of programs that form the core utilities required to make an OS useful.
Gnu can be used to describe the gnu project, the gnu license or the gnu coreutils. In this context, they mean that Linux by itself isn’t enough to be the a free desktop, and needs the gnu software to be the system they care about. (There can be controversies on whether gnu is needed or not, since it’s possible to create a distro without the coreutils, but let’s not get you confused right now)