The Server decides whether to store an audit event, based on the policies defined by the User. These policies (or Filters or Storage Policies or Audit Policies) are rules which define certain conditions. The server records all audit events that match these conditions. Policies are configuration tools that the User has at his disposal to fine tune the detail of the events to be recorded.
When an event is recorded, the server checks with its policies to see if the event need be recorded.