In this post I am going to cover the concepts of Oracle Data Guard.

Oracle Dataguard is part of Oracle Maximum Availability Architecture(MAA) which includes various Oracle technologies like RAC,ASM,Flashback, Active DataGuard and Goldengate.

Dataguard is part of MAA and used for Data protection which provides a disaster recovery solution for Oracle Databases. It also be considered as a High Availability Solution*.
For Dataguard we can  keep the DR on different servers,data centers or geographical location to provide best data protection.

In the DR environment the source database from where data is synced to target database is called as PRIMARY Database and the target database is know as Standby Database. The above picture represents simple architecture for a basic DR configuration.

DR sends the redo log files to standby database so it is also know as log  shipping based replication.
DR is a unidirectional replication which means that any changes to data made in Primary would only move to standby. No changes can be done at standby side