what's the difference between plug-in, hook and hack-in?

[Lynne]

there are no hooks that let you modify existing queries.

This is no longer true. There are hooks in many queries now.

Usually a plugin is the actually code your write and it 'plugs into' a hook in the code. If you look at an actual hook in the code, it looks like this:

PHP Code:

($hook = vBulletinHook::fetch_hook('group_dojoin')) ? eval($hook) : false; 


In that case, you would write a plug-in which hooks into the hook located at "group_dojoin".