"hook"

I consider hook to be something that your game has which appeals to the players. This is very subjective, and mainly decided by the type of player/audience you are targeting with your game.

It should be noted however, that marketing does not count as a hook. Yes it does get attention, but is far from a hook.

A hook should be something which players come back for, something which keeps their interest.

For example, a game where you play as a monster rampaging a city, and the monster which strikes the most fear wins

The hook can be the customizability of the monsters which can differentiate between look and statistics or even both, the combat system in the event 2 monsters clash, the theme itself which is an obvious draw to fans of giant monsters, as a few hook examples i can quickly think of.

But with all that said, there is no "official list of hooks". If there was, there wouldn't be any variety anymore