As stated above by default Apps will auto update and connect to the internet without asking for permission and this can really eat away at your data cap or limited megabytes if you have such a limit. The smart thing to do would be to stop Apps from auto updating as there are usually several updates within a day for various apps and update when you want and when you are connected to a home network or WiFi hot spot which is much more convenient for updating.
To turn off automatic updates:
1. Go to Google Play store and click on the menu option in the upper left of the screen.
2.From the menu look for settings and then look under general.
3. Next Tap : Auto-update Apps and choose the first option :Do not Auto-update apps.
By doing this you have just told Android not to auto update any of your apps and from now on all you have to do is open up Play Store and select an app that shows that an update is available and do so at your convenience such as when you are onWiFi connection to update your apps.