We at Beefit can set a global pixel (which applies to all products/direct sales).
Additionally, you can also set an individual pixel per product.
When the setup is done it means we send an "event" to Facebook on this pixel.
The event typically contains the following information:
"Initial purchase" when a user opens a link
"Purchase complete" when the user has actually entered their card details
Facebook can use this to track the quality of leads 😊