physical and logical backup

Hi

I havae read concepts like BACKUP. I am not able to understand what is the difference between physical backup and logical backup..?
what is the difference between cache recovery and instance recovery...?
could you pls explain me in detail....?

Thanks and Regards

physical backup is to copy for backing up all the pyhsical files that belongs to database.(like datafiles,controlfiles,logfiles,executables etc).
In logical backup,you dont take the copies of any physical things,you only extract the data from the datafiles into dump files.(ex : using export )
instance recovery:The automatic application of redo log records to Oracle uncommitted data blocks after a crash or system failure.
cache recovery:The part of instance recovery where Oracle applies all committed and uncommitted changes in the redo log files to the affected data blocks. Also known as the rolling forward phase of instance recovery.

thanks a lot balki.........