Webhooks are a simple way that an app can send an automatic message or payload of information to another app. It's the method that Stripe might use to notify you when a payment has come in, or how a support bot like Intercom notifies you about new requests in your Slack.
Simply put, Webhooks are ways for your online accounts to "speak" to one another and get notified automatically when something new happens. You'll need to know how to use webhooks if you want to automatically push data from one app to another.
Webhooks always use the POST API Verb since the other services are "Sending/Posting Data" to your Webhook endpoint. In order to receive the response from a webhook, the very first function in your Function stack should be Get All Input as shown below.
We're currently developing a logging feature that will allow you to preview incoming requests including webhooks, but in the meantime, you can use Webhook.site . It will give you a temporary API endpoint that you can use as your Webhook destination and it will show you the response when it's hit. You can see it being used in the video below (2m10s).