Webhook

A webhook is a way for one application to send real-time data to another application when something happens. It's like a phone call that an app makes to another app to say, "Hey, something just happened.

Webhooks are triggered by events and send data (usually in JSON or XML format) to a specified URL when the event occurs.

Webhook automated the messages sent from one apps to another app when something happens.

Example: 

• Imagine you have a website where people can sign up for a newsletter. When someone signs up, you want their email to be added automatically to your mailing list in another application, like Mailchimp.
• Instead of manually copying every new email address, you can set up a webhook. When someone signs up on your website, it triggers the webhook to automatically send that email address to Mailchimp. This way, the process is automated and happens instantly.

Note: There are two ways your apps can communicate with each other to share information: polling and webhooks. 

Polling is like knocking on your friend's door and asking if they have any sugar (aka information), but you have to go and ask for it every time you want it.

Webhooks are like someone tossing a bag of sugar at your house whenever they buy some. You don't have to ask—they just automatically punt it over every time it's available.