It allows the extraction of the apps within a Package.
Use it to extract iChat from your OS X install disk and then run the installer for it.
Worked on a few things for me
P
Okay so i was being stupid the other day and accidently deleted ichat from my applications folder. Is there any way to just restore this app without archiving and reinstalling the whole os.

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic