I am just giving my humble opinion and others on here may have a different opinion but I think a hook is a short part of a track catchy enough for people to recognise it immediately and 2 great examples of what I am trying to say is the intro to 'Sweet child of mine' by Guns and Roses and 'Smoke on the water' by Deep Purple.
'Nirvana' songs have great hooks and my favourite track with a 'Great Hook' is 'In Bloom'