The word ‘seal’ is used both for a matrix, an object made from hard material into which has been engraved or cast a motif and / or words, and for the impression made by a matrix in soft material. Most matrices are engraved or cast intaglio, into the surface, so that the impression is cameo, in relief. The image and words on a matrix are in reverse so that they are the correct way round in the impression. In the Middle Ages most seals have a central motif (the design) surrounded by words (the legend).
Seal impressions are used to close up documents, but their most important role in the Middle Ages was as a means of authentication.