
Explanation/Reference:
Explanation:
A webhook allows you to start a particular runbook in Azure Automation through a single HTTP request.

Box 1: HTTP Post
To use a webhook after it has been created, your client application must issue an HTTP POST with the URL for the webhook.
Box 2: RequestHeaders
Box 3: WebhookData
When a client starts a runbook using a webhook, it cannot override the parameter values defined in the webhook. To receive data from the client, the runbook can accept a single parameter called
$WebhookData of type [object] that will contain data that the client includes in the POST request.
The $WebhookData object will have the following properties:
WebhookName - The name of the webhook.

RequestHeader - Hash table containing the headers of the incoming POST request.

RequestBody - The body of the incoming POST request. This will retain any formatting such as string,

JSON, XML, or form encoded data. The runbook must be written to work with the data format that is expected.
References: https://docs.microsoft.com/en-us/azure/automation/automation-webhooks