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1.  What is a BACKUP ? What is a RESTORE ? What is  RECOVERY ?

A "backup" is a copy of the database. This copy could be a physical copy of the database (the database files are copied, so this is a physical backup) or a logical copy (the database information is copied in another format which can be "imported" again into the database to get back the old data). A logical copy of the database (or a part of it) is named logical Backup.  

When the physical files (from a backup) are copied back to the initial location is named a "restore" operation. 

When a database is restored, sometimes we need to apply last changes (from archive log files/ log files) to bring the database data up-to-date. This operation is named "recovery", because the last information is recovered. 

2.  How we can take a physical Backup ?

    a)  At the Operating System level using "copy" command ( cp for UNIX, Solaris, Linux ).  

    b) using Oracle RMAN, or other backup tools.  

3.  How can we take a logical backup ?

    a) using Oracle exp/ imp utility 

    b) the data/ code objects could be copied in a text file using different tools (like TOAD, SQL Developer)

    c) using Oracle Data Pump (10g and + )

4. Which are the steps in recovery process ?

• 1st:  Roll forward (cache recovery) : is carried out by applying all (committed and un committed) redo log records to the data files.

• 2nd: Roll back (transaction recovery) : all uncommitted transactions are reverted to its original state. This is done by reading the rollback (undo) segments.      

All this process is based on the SCN (System Change Number) which acts as an internal clock. 

More information about  this subject ( Oracle Backup & Recovery Overview ) you can get from  www.in-oracle.com