Here you can set where the disc is physically located. It could be a physical shelf, cardboard box, CD binder, disc wallet or anything you want.
The Location field consists of two part: General Location and Sub Location.
General Location (or Location) means something that can be the same for several items, for example a cardboard box, or a disc wallet. The General locations can be managed by the location manager.
The Sub Location makes the location more exact. In example above it shows the page number inside the disc wallet.