when I saw the term "horizontal joins", I immediately went to, what? what's a "vertical join?" must be a UNION, scrolled down and sure enough. Is there some

when I saw the term "horizontal joins", I immediately went to, what? what's a "vertical join?" must be a UNION, scrolled down and sure enough. Is there some reason to use non-standard terminology for posts that are trying to be in-depth, authoritative tutorials ?