The /events endpoint is the programmatic equivalent of the analytics you see in the Buttondown dashboard: every delivery, open, click, unsubscribe, and other interaction is returned as an individual event. Filter by email_id, subscriber_id, automation_id, or event_type to pull exactly the slice you need, and expand the subscriber field to hydrate each event with subscriber details.
For a guided walkthrough of pulling analytics this way, see Retrieving analytics data.