What hooks are being invoked on a node edit form
hooks are basically functions provided by drupal to developer , so as to create a communicating medium between developer and drupal.
hooks get called or render on a page when particular action associated with them take place it is more like drupal send a message to hook "describing what action drupal is doing " and hook ask developer "drupal is doing this do you want to add more stuffs or to perform any action on this action of drupal"

so depending on action taking place hooks are invoked