Non-metaphorically, the webhook endpoint is just more code on your server, which could be written in Ruby, PHP, Node.js, or whatever. The webhook endpoint has an associated URL (e.g., https://example.com/webhooks). The Payink notifications are event object. This
Event object contains all the relevant information about what just happened, including the type of event and the data associated with that event. The webhook endpoint uses the event details to take any required actions, such as indicating that an order should be fulfilled.