First-Party Audience is an audience built from data a business collects directly, such as website visitors, subscribers, customers, or CRM records.
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 retailer can build an audience from its own opted-in subscriber or customer records. Keep the collection source and allowed use documented instead of treating any purchased list as first-party data.