What is a Hook?
A hook is an entry point within a script where plugins can be executed to modify script's behavior. You can also treat it as an event which can be handled by third-party code. Cotonti literally includes PHP files registered as handlers for a specific hook. Imagine a script that has a hook in it:
$foo = 'The Lord of Foo';
$bar = 'hit the bar!';
// ...
// A HOOK is here
// ...
echo "$foo $bar";
Then consider there is a handler for that hook which can access any variables...