Each folder added to Sync receives a system .sync folder (hidden by default), which, in turn, contains the Archive folder as well as several other files:
1. .sync folder (hidden by default).
2. .DS_Store (short for Desktop Services Store) is a hidden file created by OS X to store custom attributes of a folder such as the position of icons or the choice of a background image. (appears on Apple's OS X only).
3. The Archive folder stores old versions of files which were either deleted or modified on other devices in the course of syncing.
4. ID, IgnoreList, StreamsList:
- ID represents the ID of the folder. It enables Sync to find the right peers and carry out syncing of the same folder added to Sync on other devices.
- IgnoreList enables you to specify which files should be excluded from syncing (to learn how to edit IgnoreList, click here).
- StreamsList is a file allowing you to "white list" alternate streams, xattrs and resource forks.