Does it mean that
When you issue ALTER SYSTEM ARCHIVE LOG CURRENT, Oracle Archives the log file and then switch log file?
and When you issue ALTER SYSTEM SWITCH LOG FILE, Oracle does a log switch first and then Archive it whenever ARCH has time to dio it.
No, before archiving a log, it must be switched!( finished in writing log )
For Backup you need the current log after ending backup the datafiles, because there are the last changes for the db in it which belongs to the backup;
If the Cuurent -Clause would not exist then a backup-procedure what never know having the last changes in Archived dest.
After finishing backup the datafiles the archive-dest is backuped and deleteted till the current archived log;
so when you need to media-recover a datafile you restore it and due to the archived-log you bring it to the level which was after the backup;
To understand more of backup and recovery and the concepts behind read the Oracle Database Concepts, it explains the concepts of the database;