The app exceeds the allowable size limit for downloading direct to your device via a cell network. The app download may complete successfully to your Apple id (will be stored in your icloud).
The cloud icon (with inverted arrow) is displayed when a file is available in the cloud, but it is not currently on your device. These files can be downloaded to your local machine by clicking the cloud icon.
Users may also receive a download size limit message prompting the user to switch to a wi-fi connection on the device to download the app.