Users expect relevant ads, but tracking behavior across devices, browsers, and private sessions is becoming harder as cookies disappear and regulations tighten. Understanding intent also takes more than simple clicks because viewing patterns, session length, and content preferences often shift quickly. Analyzing anonymized engagement data helps networks spot trends without exposing sensitive information. Machine learning models can predict interests, but they must avoid inaccurate assumptions that hurt performance or trust. Testing ad placement, timing, and creative formats across different audiences reveals what converts.