From the Apple Website:
Combining the power of QuickTime with Apple’s ease of use, QuickTime Broadcaster allows just about anyone to produce a live broadcast event. From a backyard birthday party to a corporate keynote speech, QuickTime Broadcaster allows anyone with an Internet connection to “virtually” attend.
QuickTime Broadcaster is Apple’s award-winning live encoding software that lets you produce professional-quality live events for online delivery—quickly, easily and affordably.