Learn hook response

The link: http://codex.wordpress.org/Plugin_API/Action_Reference/personal_options_update

gives an example,
add_action(‘personal_options_update’, ‘update_extra_profile_fields’);
function update_extra_profile_fields($user_id) {
update_user_meta($user_id, ‘my_custom_field’, ‘value’);
}

From this I interpret, the ‘personal_options_update’ action hook returns a variable ‘$user_id’ which it passes to user-defined function ‘update_extra_profile_fields’.

Now, how can i find all the variables returned by each action/filter hook. I can not find it in help, only the example in the help showed that it returns user_id. Can some one point me to a link of all variables returned by each hook.

thanks in advance.
– vv