The Content Synchronization extension is used to get content from a source instance into a target instance. For example, you can get content from a PRODuction environment sync'ed (i.e. pulled) into a TEST environment.
Workspaces as well as nodes can both be synchronised in one go. Configuration is stored in JCR and done in node /modules/content-synchronisation/config/.
The extension works as follows:
Synchronization first removes configured workspaces/nodes on the target instance, then pulls content from source instance.
After synchronization, all imported content is published.
Synchronization works in a PULL manner, so it imports content to the instance where user starts it. It does NOT push anything.