A hook can be a sung chorus line, a guitar riff, a synth melody or even a rhythm. Pop songwriters aim to introduce the hook early and repeat it often.
In short-form video, the hook needs to arrive in the first second because viewers decide quickly whether to keep watching.
Using it in a prompt
Ask for "a catchy hook in the first two seconds" for social clips, or "memorable whistled hook" when you want a signature sound.