Tracking Pixel is a small tracking snippet or image request used to record visits, events, or conversions.
It matters because most visitors do not convert on the first visit. Retargeting terminology helps teams create thoughtful follow-up sequences, avoid wasted impressions, and respect audience exclusions and privacy expectations.
Example
A page includes a tracking snippet that sends a page-view or other defined event when the relevant conditions are met. Use a testing tool to inspect the actual request rather than assuming installation alone means the desired events are recorded.