Settings-security-apps with usage access in Lollipop (what's it for)

[desertfox52001]

I saw this option 'apps with usage access' under security in Lollipop in my Z3C. I have unticked both options for now since I have no idea what's it for. I searched everywhere but found no information on this. Attached is the screenshot. Can anyone tell what's this function for? What happens if I tick them? Would they consume battery in some ways?

[Phy]

https://developer.android.com/about/versions/android-5.0.html

System
App usage statistics
You can now access app usage history on an Android device with the new android.app.usage API. This API provides more detailed usage information than the deprecated getRecentTasks() method. To use this API, you must first declare the "android.permission.PACKAGE_USAGE_STATS" permission in your manifest. The user must also enable access for this app through Settings > Security > Apps with usage access.
The system collects the usage data on a per-app basis, aggregating the data over daily, weekly, monthly, and yearly intervals. The maximum duration that the system keeps this data is as follows:
Daily data: 7 days
Weekly data: 4 weeks
Monthly data: 6 months
Yearly data: 2 years
For each app, the system records the following data:
The last time the app was used
The total length of time the app was in the foreground for that time interval (by day, week, month, or year)
Timestamp capturing when a component (identified by a package and activity name) moved to the foreground or background during a day
Timestamp capturing when a device configuration changed (such as when the device orientation changed because of rotation)