iOS 7 can automatically download and install app updates on your iPhone or iPad. Automation isn't necessarily a good thing, however, and some iOS 7 users might prefer to maintain control over app downloads. To do so, go to Settings/iTunes & App Store. In the Automatic Downloads section, flip the Updates switch to Off.
By default, automatic updates work via Wi-Fi only. To have them work over your cellular connection, too, go to Settings/iTunes & App Store and turn on "Use Cellular Data."