Straight from the horse's mouth ;-) at click here:
'Q. How does Norton 360 compare to Norton Internet Security?
A. While Norton Internet Security provides "essential security" when computing online, Norton 360 extends "comprehensive protection" to digital music, photos, and files, and maintains PC performance with tune-up functionality.
Norton 360 and Norton Internet Security provide the same essential security for antivirus, antispyware, firewall, intrusion prevention, and security inspector.
Norton 360 also incorporates the Background Scheduler feature which allows Norton 360 to work on threats, backups, and tune-ups quietly when users are not engaged with their computers.'