As others have mentionned downloading the .deb and running it will also work, but I feel nobody gave your a tldr of why you may want to follow those instructions instead, so here it is:
Those instructions configure your package manager (apt) with a new repository for this application.
The upside to that is that anytime you will look for updates, this app will also get updated.
It’s a bit more work up front, but it can pay off when you have dozens of app updating as part of normal system operations.
Imagine a world where windows updates would also update all your software, that’s what this is.
Lab grown meat is more efficient, but some place are already outlawing it before it’seven available commercially… So I’m not too sure about the direction we’re going.