Is there a difference between Wordpress Multisite (WPMU) and Wordpress, with respects to the hooks and the action reference (API)?

Question

The Wordpress documentation isn't clear about this: http://codex.wordpress.org/Plugin_API/Action_Reference

What I specifically need to know is whether add_action("publish_post", "myCallbackFunction") is a hook that will apply across the entire Multisite network, or simply on an individual page (or merely for admins).

What I want is that myCallbackFunction is triggered whenever any of the bloggers on the Multisite network clicks the button to publish a blog post.

Ref: http://codex.wordpress.org/Plugin_API/Action_Reference/publish_post

Answer 1

'publish_post' is not attached to a single page (even on a non-Multisite install).

The 'publish_post' hook is run by the WordPress core whenever a post is published. As long as this hook and the callback are part of an active theme or plugin (that exists across all multisite instances), they will run whenever a post is published.