Webhook

A webhook in web development is a method of augmenting or altering the behavior of a web page, or web application, 
with custom callbacks. These callbacks may be maintained, modified, and managed by third-party users and 
developers who may not necessarily be affiliated with the originating website or application.

Webhooks typically are used to connect two different applications. 
When an event happens on the trigger application, it serializes data about that event and sends it to a webhook 
URL from the action application—the one you want to do something based on the data from the first application.

When we talk in the context of api a webhook is an concept that's growing in popularity. ... A webhook (also called a web callback or HTTP push API) is a way for an app to provide other applications with real-time information. A webhook delivers data to other applications as it happens, meaning you get data immediately.