I've just started with Ruby and Rails using a book called Ruby on Rails tutorial 3.. this article didn't provide anything that I found useful. It reminded me of a lecture on Java I heard about in Computer Science 101 day 2.
Utility is relative to curiosity. A butcher might be interested in animal husbandry, but maybe they just want to cut steak. To a Rails dev, this is all "what happens to the cow before it's steak" stuff.
I'd recommend coming back and reading it when you've learned a bit more Ruby then. If you've "just started" then you probably don't yet have the experience in Ruby to understand what it means.
I understand that at a first glance this looks like basic stuff that doesn't explain anything useful, but with a bit more experience you'll see that it's fundamental to understanding how Ruby will react in certain situations.