Glossary
Pixel
A piece of code on a page that reports events to an ad platform or a tracker: a view, a lead, a purchase. The platform uses it to optimize delivery and build audiences; the affiliate uses it to feed conversions back to the algorithm.
Also called: Meta Pixel, tracking pixel, conversion pixel.
Meta's Pixel and Google's tag are the main ones. Placed on a lander (or fed through a server-side integration), they tell the platform which clicks converted, so it can find more people like them. On grey campaigns the pixel is fed with events that pass review, or through a server-side API to avoid the page showing the real event.
A pixel is client-side and cookie-based; a postback is server-side. Affiliates use both: the pixel for the platform's optimization, the postback for their own numbers.
Related terms: Postback, Retargeting, Tracker, Landing page.