The desktop client is a program that allows you to store your data from the cloud locally on your computer or laptop. The client runs in the background and automatically synchronises your data so that you always have the latest version of a file available on all devices.
The app for mobile devices is ideal for viewing and sharing files on the go. You can upload, delete and move files (such as photos). However, because mobile devices usually have limited storage space, your files are not automatically downloaded. A file is not saved on your device until you manually access it.