A product is one Atlassian Marketplace app that Marketplace Events watches — for example a Jira or Confluence app you publish. It is the unit of syncing and the unit of metering.
Each product is tied to one Atlassian credential (the developer-space token used to read its licences and transactions) and has any number of destinations (connections) that receive the events synthesised from that data.
A product moves through a small set of statuses: pending_backfill (added, awaiting its first history load), active (syncing normally), payment_required (over the free event limit and paused), disabled, and error.
Related: Destination · Sync run