Called Event Log in the dashboard. An organization-scoped record of who did what and when: membership changes and app lifecycle events, in one place, visible to Admins.
It exists for the moment you need to answer a question after the fact rather than in real time - who invited a member that shouldn't be there, when an instance was last upgraded, why an app is suddenly in an error state - without having to reconstruct the sequence of events from memory or from scattered notification emails.
See Concepts › Audit log for what specifically gets recorded.