database duplication VS database replication
Database duplication generally refers to restoring a physical backup of a database to a different server (preferably using RMAN).  That is normally done periodically to refresh lower environments from production.

Database replication generally refers to the process of copying a subset of data from one database to another on an ongoing basis.  Replication generally implies that the data is being copied from one production database to another production database (or a test database to a test database, etc.)