This feature is for setting an automatic Task state update once the Driver is within the radius of the location.

Enabling it can be done in Configuration ⇒ Driver App ⇒ Auto-arrive geofence.

It's also possible to customize the location radius of when the auto-arrive geofencing will trigger. For example, if you set a 100 meter radius, this would mean that the Task state will automatically change to Arrived once the Driver is within 100 meters of the delivery location.

Click Save once the changes have been added.

In case you have pre-set email or SMS notifications which trigger when the Task's state is changed to Delivery Arrived,, those notifications will be sent once the Task state has been automatically switched to Delivery Arrived when the Driver is within the specified vicinity of the delivery location.

Disabling Drivers from updating Task state updates outside of the Task location radius can be done in Configuration ⇒ Driver App ⇒ Prevent task status updates based on geofence.

It's also possible to allow the Driver to update the Task state regardless, but this will prompt a confirmation dialogue box before the update is made.

In case you want to have more flexibility over how geofence behaves, and you would still like to give your Driver the option to override the Geofence restriction, you can do so by enabling the Geofence override option.

This can be toggled on only if the option to Prevent update outside of geofence option is enabled as well. All the state update Geofence overrides will be recorded and displayed in Task History.