Ios8 UIBackgroundFetch导致DidReceivereMotenofication

DidReceiveEmoteNotification调用中completionHandler中UIBackgroundFetchResult的含义是什么？也就是说，SDK使用UIBackgroundFetchResult的目的是什么

 - (void)application:(UIApplication *)application didReceiveRemoteNotification:(NSDictionary *)userInfo fetchCompletionHandler:(void (^)(UIBackgroundFetchResult))completionHandler 

具体来说，如果我返回以下内容，不管我在收到推送通知时是否已获取新数据，会发生什么情况

UIBackgroundFetchResult fetchResults = UIBackgroundFetchResultNewData;
if (completionHandler) {
    completionHandler(fetchResults);
}