I'm not 100% sure. But some what sure. It's when you download from App World. They "come back" just in case you want to redownload them.
The arrow representing "bring back" sort of speak.
Posted from my CrackBerry at wapforums.crackberry.com
If you want to remove the "Archived" app from your BB then you also have to delete it from App World. Once you do that the app will disappear from your BB.