Hook
The opening line or first few seconds of a post, written to stop the scroll and earn the rest of the attention.
A hook is the very first thing someone reads or sees — the opening line of a post, the first frame of a video, the headline of a thread. Its only job is to interrupt the scroll long enough to buy the next sentence. If the hook fails, nothing else in the post matters, because almost no one reaches it.
Hooks work by promising payoff: a sharp claim, a question, a number, a tension that the caption then resolves. Pair a strong hook with a clear call to action and you've bookended the post with its two highest-leverage lines.