A duplicate (auxiliary) database is a copy or subset of the target database and has a unique DBID. It is independent of the primary database and can be registered in the same recovery catalog as the primary database. A duplicate database is useful for testing or demonstration purposes.
If the duplicate (auxiliary) database already exists in the destination computer, it will be overwritten. The duplicate database is created from the full backup of the database with the logs. If you want the latest data in the duplicate database, make sure to perform a full backup with the log files before creating the duplicate database.