As used in the creative arts, whether it's a song or an article it's a phrase or a thought that makes the reader/listener take notice, right? It makes them want to read/hear more. When I say, My uncle touched the floor of the ocean - and lived to tell about it!- that's a hook in the style of the National Enquirer. If my song says, Out the window I went, into the rain and the dark- that's a hook.