Many apps can refresh their content in the background. This means they’ll always be up-to-date when they’re opened. Of course, this can affect battery life. To stop this, open the Settings app, select General, then Background App Refresh.
You can turn it off for all apps at the top of the screen, or turn it off for individual apps from a list below. If you use an app that requires your location, then leave Background App Refresh on for that app in the list so it can continue to track your whereabouts.