What is a webhook?
A webhook is an automatic notification that one application sends to a web address the moment a specific event happens, such as a form submission or a paid invoice, so another system can react right away.
With a regular API call, your software has to keep asking, "Anything new?" With a webhook, the other system tells you as soon as something happens. The sending app is configured with a destination URL and a list of events. When an event fires, it sends a small package of data, such as the customer's name, the amount paid and the time, to that address.
Webhooks are what make fast responses possible. A new web enquiry can trigger a text to the on-call coordinator within seconds instead of waiting for an hourly sync. Integration platforms like Zapier, Make and n8n can receive webhooks without any code, and many scheduling, payment and form tools can send them.
The catch is that webhooks are fire-and-forget by default. If the receiving end is down or misconfigured, the message may be lost or retried a limited number of times, depending on the sender. Anything important should have a backup check, such as a daily report of records that did not sync. The destination URL should also be treated as sensitive, because anyone who knows it may be able to send fake events.
Example
For example, a home care agency's website form sends a webhook to n8n whenever a family requests a consultation. n8n creates the lead in the CRM and texts the intake coordinator on duty. A morning check compares form submissions with CRM records so no request slips through if a webhook fails overnight.