What is "briefadel"

Briefadel (in German) or brevadel (in Danish, Norwegian, and Swedish) are persons and families who have been ennobled by letters patent. The oldest known such letters patent were issued in the middle of the 14th century, during the Late Middle Ages. Briefadel contrasts with Uradel, whose enoblement predates issuing of letters patent. The term dates to the early nineteenth century.