We've already covered selectors quite a bit. For instance, you already know that $("p") will select all paragraphs on a page. Not just the first one or some random one, all of them. You can easily imagine there may be many of these on a page. Now imagine what happens when you do:
If you want to, you can still write the loop yourself. That would perhaps look like this, using jQuery looping methods:
That's just about the same thing. Not necessarily, but you could. That's explicit iteration.
Sometimes you need to do explicit iteration. Basically, if we need to access the value of this and do something special with it, we'll need our own loop construct to work with.
The example in this screencast was counting the characters in list items and append that to the end of the string. We'll need explicit iteration for that.