Groups visitors into cohorts by their behavioural archetype — Focused buyer, Frustrated bouncer, Calm researcher and so on (the same taxonomy as the Behavioral Fingerprint engine) — and tracks each cohort's engagement AND retention over time: repeat rate, 1-day and 7-day return, and average sessions. Answers which behaviours come back and which churn. Reads the behaviour Visitor Intelligence already records — no extra tracking, cookieless. Feeds the Cohort panel of the Visitor Intelligence hub.