Reference on Core hook() functionalities

Hook() functionalities are part of core module. If you wish to integrate or call up the existing core module functionalities, you'll need to know all available hook() names. The implementation of hook() can be done via overriding method. If your module wish to use the core hook() functionality eg hook_help(), you can just override the existing function name of hook_help() to your own customised name but retaining the functioname which is _help whereas the name of hook is changed to your modulename. Example hook_help() is changed to modulename_help().



The link to description of all available hook name is here