Apart from being open source what is Linux? Could I not create my own operating system that is different to windows or Macos and call it Steve, again there might be an awnser for this and sounds stupid but its more out of curiosity.
It is. The other person is confusing it with Solaris, which is a Unix derivative based on a mix of System V Unix and BSD.
Linux is a Unix, but Unix is not Linux. Solus is a Unix, as is MacOS (a really bad one), and BSD.