The NIE
Foreigner Identity Number: a letter, seven digits and a check letter. It is assigned once and stays with you for life.
You may need one without living in Spain: to buy property, inherit or work. You request “asignación de NIE” and receive it on paper, not as a card.
The TIE
Foreigner Identity Card: a physical document with your photo, signature, NIE, permit type and expiry date. It grants no rights itself: it documents a permit already granted. That is why it comes after the decision and expires with it.
The differences
Nature: number versus card. Expiry: the NIE never expires; the TIE does. Fingerprints: always for a TIE, except under-sixes. Fee: each has its own line on 790 012.
EU citizens
Citizens of the EU, EEA and Switzerland receive the registration certificate, with no photo and no fingerprints. Their non-EU family members do get a card, with fingerprints and a 12,00 € fee.
General information, not legal advice. For questions about your own case, check the decision you were sent or ask a professional.