Active is a state that indicates which application instance is operating the system.
Standby is another instance state that indicates that the application instance is not performing any operations and is waiting to take over. (As opposed to Master/Slave applications where the slave instance can still perform operations
Example: toolpack_sys_manager is an active/standby type application. The active toolpack_sys_manager is the only instance that takes action on the whole system, the standby toolpack_sys_manager waits to takeover if the active toolpack_sys_manager fails.