payload(in json format)—and are sent to a unique URL. You can create such URLs in Directual to receive those messages.
Integrations/Webhooks/folder (you can also find a link to it right here, in webhooks table). The first object is created by Directual itself — that one is for test purposes.
id— usual unique field
body, headers, urlData— fields in JSON format. One or a few of them contain data (depending on a specific third party service).