&key and how it's used

[Yves S. G. <you...@gm...>]

Hi all,

   I'm reading this chapter of gigamonkeys.

http://www.gigamonkeys.com/book/practical-a-simple-database.html

2/3 down the page, I see the following methods:

http://bin.cakephp.org/view/1169646936

Now, where I'm drawing a complete and utter blank is 1) how *db* is
accessed, that's where all the data is held and 2) what the heck is &key?

If I'm missing something absurdly obvious, please feel free to point it out.