A Pixel Event is a specific user action tracked by the Meta Pixel, such as a page view, add to cart, initiate checkout, purchase, or lead form submission. These events send signals to Meta’s algorithm about which users are most likely to complete the desired action, and are the primary fuel for campaign optimization. Standard events are predefined by Meta; Custom Events allow tracking of any action specific to a business. The quality and volume of pixel events directly determines how fast an ad set exits the learning phase and begins performing efficiently at scale.