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".
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.