Sudo (superuser do) allows a system administrator to give certain users (or groups of users) the ability to run some (or all) commands as root while logging all commands and arguments.
In Solaris you don't find sudo (though its available on sunfreeware.com) because we have RBAC. For details on RBAC see Ben Rockwood's blog entry: http://www.cuddletech.com/blog/pivot/entry.php?id=362
Root privilege is required during Oracle RDBMS installation for running root.sh. Refer to Metalink Note 413855.1 Can root.sh be run as sudo. The other time when root access is required is when you are installing a fresh instance of E-Business Suite. On unix, root user starts the rapidwiz (Rapid Install) process which installs E-Business Suite.