The description only labels this the policy's 'action' property, but its role in UCS Manager's Server Discovery Policy is to hold the discovery-qualification action -- values such as ImmediateOrIfConnectedFabricInterconnect, IfConnectedFabricInterconnect, or UserAcknowledged. This single setting decides whether a freshly racked blade is inventoried the instant it powers on or sits idle until an admin manually acknowledges it, so checking it is the first step when a new server isn't showing up. A domain set to ImmediateOrIfConnectedFabricInterconnect will auto-discover a blade within seconds of insertion, while one set to UserAcknowledged leaves the same blade pending until someone clicks Acknowledge.