Comma notation in jQuery?

Question

So I've taken a look at this some comma notation in this tutorial using jQuery. The link is here: http://jqueryfordesigners.com/coda-popup-bubbles/.

After looking at all the selectors on the jQuery site, I can't seem to find out what this ', this' notation represents.

Any answers?

Here's a quick snippet:

var popup = $(popup, this).css('opacity', 0);

Answer 1

the second argument in the selector is a context for search .. $(a,b) is the same as $(b).find(a)

more information can be found right here