You can also select custom HTTP requests as a "Data Source". This is a universal way to receive custom requests from various services.
Depending on the selected source, you will have access to a list of fields that will be sent for processing.
For example, if you selected Facebook lead forms as the source, you will have access to at least the following fields:
Lead ID, Creation date and time, Ad ID, Ad name, Ad set ID, Ad set name, Campaign ID, Campaign name, Form ID, Form name, Page ID, Page name, Full name, Phone number.