It is distributed because everyone has a copy of the full source (nobody's copy is the copy) and you can push and pull from any machine. I can literally push from my laptop to yours (if I have an account on your machine) and you can pull from mine to yours. Github's copy of my code is exactly the same as Dave's copy. It just happens to have a fancy web interface.
In practice of course almost nobody uses Git to push/pull from other people's personal machines (I think I've done it once ever). But it's pretty common to push and pull from multiple hosted repos (e.g. Github and an internal company Gitlab). I imagine doing that sort of thing with SVN would be a right pain.
