Physical Standby Database:
A physical standby database is a exact copy of the primary database. Oracle uses the primary database archive log file to recover the physical standby database.

We can open a physical standby database in read only mode, but at the time of read only mode, the received logs will not be applied.

When the logs are applied, the database is not accessible.

Logical Standby Database:
Logical Standby database are opened in read/write mode, even while they are is applied mode. That is, they can be used to generate reports and the like. It is indeed a fully functional database.