Webhook
A webhook is a notification one system sends another the moment something happens, delivered as an HTTP request to a URL the receiving app registered. In Instagram automation, Meta's webhooks tell a tool about new comments, messages, and story replies in real time, so responses go out in seconds rather than on a polling delay.
Why it matters for creators
Webhooks are why automation can answer in seconds. The moment someone comments or replies to a story, Instagram pushes the event to your tool — there's no waiting for a periodic check. The person gets the link while they're still looking at the post, which is when a reply is most likely to be read and acted on.
None of it needs your attention: the tool registers its webhooks with Meta and keeps them healthy. The word is worth knowing mostly so the plumbing isn't mysterious — when a tool says "real time", webhooks are the reason it can.