What is introduzioni?

Some articles on introduzioni:

Gloria (Vivaldi) - Introduzioni
... Further information Introduzioni (Vivaldi) As with other choral pieces the composer wrote, Vivaldi wrote many an introduzione (introductory motets) that were to be ... Four introduzioni exist for these Glorias Cur Sagittas (RV 637), Jubilate, o amoeni cori (RV 639) (the last movement of which is compositionally tied with the first movement of RV 588), Longe Mala ...
Introduzioni (Vivaldi)
... Eight introduzioni by Antonio Vivaldi survive, each in three or four movements ... The texts of introduzioni are non-liturgical, but sometimes paraphrases of liturgical texts ... In the Ryom Verzeichnis, Vivaldi's introduzioni are numbered from RV 635-642 ...