file values sent in a track event, as a base 64 encoded string. These values can then be used to send email attachments.

File type user property to capture to send receipt’s for a purchase. Then, this file will be assigned as a user property value, which is accessible in templates.
Like
Performed user properties, File user properties are calculated synchronously from within event entry Journeys. This allows you to include files in the same track event used to trigger journeys, and guarantee that the file is used to render message templates for those journeys.
