Webhook

A webhook is an automatic HTTP request that one application sends to another when an event happens. Instead of your server asking another service again and again whether anything has changed (polling), the service calls a URL you provide as soon as the event occurs, usually with a JSON payload describing it.

Webhooks are used for payment confirmations from gateways such as Razorpay and Stripe, new commits on GitHub, form submissions and chat notifications. The receiving endpoint should verify the request's signature, respond quickly and handle the same event arriving more than once.