standby:database is in stand by mode means only read purpose available for selection.generally this state is kept for logshipping.DML commands doesnt work in this mode..

norecovery:the database is looking for additional backups while restore it means u can add additional backups to database online from point of failure.mirroring we keep database in a no recovery(restoring mode).

database becomes non-operational

recovery: database is in online mode,operational mode,not possible to apply furthur backups