Imprint is an ability word.
Cards with imprint are all permanent cards. When one enters the battlefield, the imprint triggers. The ability will exile a card from a certain zone. The zone and card are different on different cards. Take Prototype Portal as an example. When imprint triggers, you can exile an artifact card from your hand. That means you take an artifact card in your hand and imprint it on Prototype Portal. You should put the imprinted card on the imprinter.
Now, Prototype Portal can make tokens that are copies of the imprinted artifact. Not all imprinters do this, however. Some imprinters make you exile your cards that are already on the battlefield, while others can even exile your opponents permanents.
If the card that had imprint leaves the battlefield, as if it were killed by Shatter, then the imprinted card stays in exile. If somehow the artifact with imprint is returned to the battlefield, the card that was imprinted before is no longer imprinted on the returned artifact.