Why are these multiple selectors required?

Why are these multiple selectors required?

Hello,

I am new to jQuery and to the forum, so a big hello to everyone.

I have come across a nice little piece of code here: http://tympanus.net/codrops/2009/12/08/beautiful-slide-out-navigation-revised/ which creates a slide out navigation panel.

The jQuery code located just before the comments on the page is short and I easily understand what it does, but what has me spooked is why do we need this multiple selector:
  1. $('a',$(this))
instead of using just this single selector:
  1. $(this)
I would love to know why.

Thank you
Crouz