A webhook is a way for web applications to communicate with each other in real time. It is essentially a method for automatically sending data from one application to another whenever a certain event or trigger occurs in the first application.
When a webhook is set up, the first application (often called the "sender") will send a request to a URL specified by the second application (often called the "receiver") whenever a particular event occurs. The request will contain relevant data about the event, which the second application can then use to perform an action or trigger another event.