There are basically two important process on standby database.
MRP - Managed recovery process - For Data Guard, the background process that applies archived redo log to the standby database.
RFS - Remote File Server process - In Data Guard, the remote file server process on the standby database receives archived redo logs from the primary database.
Following are the key processes in a DATAGUARD setup
If DMON is not there, then the configuration is not a DATAGUARD configuration. It is just a primary/standby setup
For detailed information. Please refer