In period, scribes were the people who could write. Often, they were monks or nuns who worked in a scriptorium to produce beautiful illuminated books and manuscripts. Later in period, scribes became more secularized, and scriptoria became more like the artist workshops that also cropped up in the Renaissance.
Scribes in the SCA
In the SCA, scribes are the volunteers who produce the beautiful award scrolls that are handed out during courts. The calligraphy and illumination on the scrolls is often on par with a medieval book of hours or grant of arms.
Origins of Error
Scribes (both medieval and SCAdian) are, among artisans and craftsmen, unique in that they have a patron demon, Titivillus, who supposedly induces them to make errors in transcription.