# Concept: Event

An **event** is one canonical lifecycle moment synthesised from how a licence changed between two syncs — *trial started*, *trial converted*, *licence renewed*, *upgraded*, *downgraded*, *churned*, and the rest of the fifteen types. It is the product's whole output: the thing delivered to every destination.

Events are **synthesised, not stored upstream** — Atlassian gives us licences and transactions, and the engine diffs successive snapshots to decide which events occurred and in what order. Each event carries an entitlement number (which licence), an occurred-at time (when Atlassian says it happened), and a properties body (the payload).

Each event fans out into **deliveries** — one attempt per enabled destination, each with its own HTTP status. A delivery that fails after retries becomes a dead letter.

Related: [Sync run](/concepts/sync_run) · [Licence](/concepts/license) · [Destination](/concepts/connection)