QD Tag/label makes the product (a TV, or coffee, or tissue paper boxes) identifiable and prevents counterfeit product in the supply chain. That's end to end track and trace.

QD physical key allows one user access to his blockchain account.
Its purpose is to be an uncloneable system that cannot be hacked.
It is optical so would be read by a reader/scanner/camera, and possibly in the future by your mobile phone.

So there are at least two products to sell users of the QDX Ledger.