I use Avast Antivirus. When I do a full scan, I'm asked whether to 'delete' an invader or 'move to chest'.

The 'move to chest' is the recommended action. Why is that? I would think DELETE would be the way to go. Could someone explain to me why 'move to chest' seems to be the better way to go?

Also, should I delete what's in the 'CHEST' at one point? Or do I just leave it in there forever?