A document from the Cabildo Catedralicio (Chapter) of Santiago that certifies that the pilgrim has completed the route. It is written in Latin. To get it you have to present the stamped credential. You should have arrived in Santiago after 100 kilometres on foot or 200 by bicycle, as a minimum requirement.
A document that provides evidence that the holder has the status of pilgrim. You can get in the associations, guilds and shelters appointed by the church of Santiago. Its price is symbolic, around 2 euros. It does not give you any rights to anything, but it does indicate that you are a pilgrim. It should be stamped twice a day in the places along the Pilgrim's Way; indeed, some guesthouses only accept pilgrims with the credential. If you cannot get it, you can put the stamps in a diary alongside the dates you stopped in places along the way.