Once you mark a folder or file as a favorite, the content is synced locally to your device so that you can quickly access it, even when offline. You can interact with these files just like any other file; however, as they are always stored on the device, there is never any worry about having to download the file while on the go.
Since large folders and files can take a lot of space, as well as time to download, you should only favorite those folders and files that you wish to access quickly. Favorited content is continuously synced when the app is actively running either in foreground or background and your device is connected to the network.
To view your favorite items, tap Favorites from the top menu, as shown below. From within the Files screen, all favorited items are marked with an orange star. You can tap the menu again to select the Files view.
The contextual options for the favorited files and folders remain the same as in the files view.