Update folder_permission.md

invisible folder permission and syncing

en/sharing_collaboration/folder_permission.md

@@ -51,4 +51,12 @@ In the first case, you only want James to see folder B, the other users in the g
 
 This way the permission for James will overwrite the permission set to the group, making B only visible for James.
 
-In the second case, you don't want James to see folder B. The solution is simple: you just set sub-folder invisible for James.
+In the second case, you don't want James to see folder B. The solution is simple: you just set sub-folder invisible for James.
+
+## Folder Permissions and File Syncing
+
+Folder permissions have the below effects to file syncing:
+
+* If you set read-write or read-only folder permissions for a sub-folder in a shared library or shared folder, the files in the library/folder can be synced with Seafile client and SeaDrive client.
+* If you set online-read-write or online-read-only folder permissions for a sub-folder in a shared library or shared folder, the files in the library/folder can **NOT** be synced with Seafile client and SeaDrive client.
+* If you set online-read-write or online-read-only folder permissions for a sub-folder in a shared library or shared folder, the library/folder can be synced with Seafile client and SeaDrive client. **But the invisible sub-folder will not be synced.**