What do the numbers mean at the end of add_action('save_post')...?

Question

I've seen on a few tutorials that there are numbers at the end of the call to save Custom Fields/Meta Boxes on the save_post hook. For example, in the WordPress Codex it gives the following example:

<?php add_action( 'save_post', 'my_save_post', 10, 2 ); ?> 

What do the 10 and 2 mean at the end?

I've tried talking to an "expert", but they've been of no help ;)

Answer 1

The 10 is the priority (relative to other added actions) and the 2 is simply the number of arguments that my_save_post() will accept.

See the codex.