List-Based Retargeting is retargeting based on uploaded customer, lead, or subscriber lists.
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 business can use an eligible list of existing customer identifiers to create a matched advertising audience. The platform’s match result will not necessarily include every record, so the uploaded list size is not the same as the reachable audience size.