You open a jar of sauce. You don't use all of it, so you put the rest in the fridge.
The jar says use within one month.
But in a couple of weeks, you have forgotten when you put it in the fridge.
So you throw it away.
Not any more.
You add a Yokti QR code sticker to the jar and activate it.
Now, all you or anyone needs to do is scan the QR code to check how long the jar has been opened.