Sailpoint IIQ : Sailpoint IIQ refer to Sailpoint Identity IQ.
Identity Cube: Identity cube store all the information about an Identity. Identity cube refer to each unique identity stored in SailPoint Identity IIQ.
Application: Application is refer to target resource or resource which is going to integrate with SailPoint for identity and Access management. For Example : Active Directory (AD). We integrate Applications for identity and Access Management.
Authoritative Application: Authoritative Applications are like trusted application in SailPoint, these are trusted in the sense of trusted identity data SailPoint rely on. Like HR Management System, we know HR data from some particular firm will have trusted data of employee in that firm.In SailPoint we have to mark some application as Authoritative application