Most of the files on your local Cloud Drive are synchronized with place-holders or representations of the full file. This spares data transfer capacity and improves speed, as files are only fully fetched when they are accessed by the user. When a folder is changed to “offline” it forces all of the content to be pre-fetched immediately. Contingent upon the size, this may take some time, but after the initial synchronization, changes to the folder will be downloaded as needed to keep up the offline status.
To add an offline folder, pick Offline Folders from the console menu and click the “+” icon (1). You will then choose a folder (2) from the shared folders on the cloud, click Enable Offline Access (3), select Yes in the confirmation dialog (4), and the contents of that folder will be pre-fetched (5) for access while offline.