If you run out of storage, it automatically outsources files to make room for new ones. When you need outsourced files back, SCS re-downloads them immediately.
SCS moves your data to and from the cloud (Google Drive), thus effectively increasing the total storage space of your phone.
SCS offers you a Drop folder to move files easily from your desktop computer to your phone, making MTP obsolete.
There has been a lot of confusion about what actually happens to files and a lot of people fear to lose their files. If you do too, please read on and let me explain, what SCS does with your files:
1) SCS uploads all the files it is allowed (those in the watched folders, which you control) to a Google server (Google Drive).
When you create a new file, it is also uploaded. When you delete a file on your phone, it is deleted on Google Drive too. This creates a live backup of all your files, which can come in handy anyway.
2) Now, when you run out of storage (meaning you go below the “Keep Free Minimum” defined in the “Storage Overview” of the app’s settings), SCS shows you a notification, a so-called “Space Alert”.
If you click on this notification, SCS will give you a list of files it thinks would be good to outsource (files you did not use in a long time, for example). Only files that are online on Google Drive are displayed here. So files displayed to you exist both offline and online.
If (and only IF!) you click on outsource, the contents of these files will be overwritten with 0 bytes. This makes room for new files on your phone, while still holding on to the version of the file that is online on Google Drive.
3) As soon as you or any application try to open an outsourced file, this file is re-downloaded to your phone.
Does SCS delete files on my phone?
No, SCS does not delete any files on your phone EVER. It merely overwrites local files with 0 bytes, if and only if this file is backed up.