A jargon-free guide to the bare number, the green certificate and the residence card.
The NIE is simply the number. EU citizens walk away with a green certificate; non-EU citizens receive a TIE card. All three end up lumped together — confusingly — under the single label "the NIE".
Which of the three you actually need decides whether you have to queue in the capital at all. The bare number can be issued at a distance — AnchorLess obtains the number without a visit, for one — whereas the card means fingerprints given in person at the Palma office, and there is no way round that.
If you are from outside the Union and putting down roots in Palma for the long term, the document you will eventually hold is a TIE card bearing your NIE number.