Geodatabase replication allows you to create copies of data across two or more geodatabases such that changes to the data may be synchronized.
Nathalie,
As mentioned in the links:
Replicas and geodatabases:
http://resources.arcgis.com/en/help/main/10.1/index.html#//003n000000vp000000
We need atleast two geodatabases for this functionality.
Regards,