The illustration is for Backup Anywhere mode for Dataguard.
It shows squares for two data centers labeled Local and Remote. Each data center square has the database DB-a and one recovery appliance, labeled RA-x and RA-y.
The local database has an arrow going to its RA-x for backups, and second bi-direction arrow going to the remote database, labeled Data Guard Redo.
The remote database has an arrow going to its RA-y for backups.
The local RA-x has an arrow to the remote RA-y, indicating Replication.
The remote RA-y has an arrow to the local RA-x, indicating Replication (no initial full).