In a template you can choose between "all item" and "selcted item" synchronization for all libraries and lists.
You can select the items which should be synchronized or not be synchronized.
The sense behind this feature is that the items which are duplicated in your workspaces not longer will be added to the list or library.
These works also in all subsites.
All item synchronization
With this option all items will be synchornized or not be synchronized.
Selected item synchronization
With this option only the items which are selected will be synchornized or not be synchronized.