Allegati contain all the documentation presented to fulfill a vital record. Allegati are very important for marriages because the include the birth certificates of the spouses and very often their parents death certificates
Just to add to what Livio has said re the Allegati: I’ve just recently come across Allegati for one of my Italian towns and I think they are brilliant and would recommend anyone going through these. (They are a treasure chest!)
Like Livio has said they include the birth records of bride and groom and also death records of parents who may have died from which you may extract further vital info. AND not only these records but some of my Allegati have included the groom’s grandfather’s death record (father’s father “avo paterno dello sposo”) which consequently has given me two more sets of “grands” that I did not know previously – my great, great, great, great and great, great, great, great, great grandparents (mid 1700s). (An extremely exciting and rewarding find!) Allegati will include other records or extracts of records also e.g death record of previous spouse if either bride or groom is widowed.
The Allegati that I have gone through has a cover page and then a copy of the “Atto di solenne promessa di matrimonio” The Atto di solenne promessa di matrimonio includes on the front page a list of the supporting Allegati which then follows. I have found this very helpful. Your records might not have this though but the cover page and Allegati are definitely there.