Can somebody please explain webhooks (for dummies)

[Mr Lucky]

I am trying to get bounce notifications from Postkark SMTP provider. I have looked for simple guides on how to do this via a webhook, but they all seem to assume you know what they are on about already.

Is there a simple guide anyone knows of, or maybe just explain. It looks simple enough.

Under add webhook I have to

• Put in a webhook URL. But I fall down at the first hurdle - ie what should I put there?
• Custom Headers and basic auth - no idea about this???
• Choose event. That's easy enough as I can tick bounce
• Then Test your webhook URL - dropdown for Delivery, Bounce, Spam complaint etc. (so I choose bounce)

Then there is some code:

{
  "Metadata": {
    "example": "value",
    "example_2": "value"
  },
  "RecordType": "Bounce",
  "ID": 42,
  "Type": "HardBounce",
  "TypeCode": 1,
  "Name": "Hard bounce",
  "Tag": "Test",
  "MessageID": "00000000-0000-0000-0000-000000000000",
  "ServerID": 1234,
  "MessageStream": "outbound",
  "Description": "The server was unable to deliver your message (ex: unknown user, mailbox not found).",
  "Details": "Test bounce details",
  "Email": "john@example.com",
  "From": "sender@example.com",
  "BouncedAt": "2020-03-19T12:31:49.8579524Z",
  "DumpAvailable": true,
  "Inactive": true,
  "CanActivate": true,
  "Subject": "Test subject",
  "Content": "Test content"
}

OK, so far looks like I could start experimenting (maybe I just edit that code with my email address???? - but still don't know what I put as the URL at the top