Open Standby Database for Querying

Opening a Standby Database in DataGuard for Querying in Read Only mode.
The standard method is to halt (suspend) Recovery at the Standby so NO fresh Redo is applied to the Standby. You see data as of the point in time when recovery was halted.
The method using the Active DataGuard Licence (paid feature) allows you to continue applying Redo (transactions) to the Standby while you query it. Thus, the Standby will always be up-to-date (i.e in-sync) with the Primary when you query it.