With an API, one system asks another: “anything new?” A webhook works the other way — the system itself sends a request (an HTTP call) to a set address as soon as something happens: a new order, a payment, a signed document.
Webhooks are a fast, efficient building block for automation. For security, the receiver should verify the message signature (e.g. HMAC) so it doesn’t accept forged requests.
Example
When a document in iComp needs action, a webhook notifies n8n, and n8n sends a Telegram message.