A small iCloud icon appeared on my iPhone home screen. Why does iOS show a white cloud next to app names on my iPhone, iPad or iPod touch?
If there's a cloud symbol next to an iOS app name, this app has been offloaded to increase storage space on your device.
One of the features included in iOS 11 and later is app offloading. Offloading apps increases storage space by removing unused apps. However, unlike deleting apps, offloading keeps app data stored on your device. This means when apps are reinstalled they can be restored to their last used state.