These terms refer to features that manage data usage after your plan's data allowance is exhausted. They allow you to control whether to continue using data at standard rates or to stop data service to avoid extra charges.
1) When active, you can continue using data services after you've used up your plan's data. Standard data rates will apply for this additional usage.
2) If not active, your data service will stop as soon as you reach your plan's data limit. This prevents additional charges for data overage.