By tracking what apps you have installed on your iPhone advertisers try to target consumers and offer specific ads. An example: if you have a golfing app installed you are more likely to be the target of golf related advertising.
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You can limit ad tracking or reset your advertising ID.
iOS 7 includes a feature called "Background App Refresh" that allows apps to refresh their content in the background, so apps wake up periodically, and download the latest content when running on Wi-Fi.
This can be a drain on your battery life, and in iOS 7 the default is set to on.
According to Apple "iOS learns patterns based on your use of the device and tries to predict when an app should be updated in the background.
It also learns when the device is typically inactive, such as during the night, to reduce update frequency when the device not used.
To disable this feature, visit
Settings > General > Background App Refresh.
Here, you can turn off the entire function or just disable that apps you don't need to refresh on an automatic basis.