They are often said to have miraculously "fallen from sky", claim protection for owners of a copy (encouraging memetic replication) and punishment for disbelievers.
Some authors reserve the name for Christian apocryphal documents, but similar pieces are found in Islam, Hinduism and pre-Christian religions.
In the Pennsylvania German community, they are part of Pow-wow tradition and contained Bible verses and other charms and assurances that their owners would be protected from death, injury, and other misfortune.
A hand-written letter produced by a respected Hexenmeister or Braucher is regarded as a powerful talisman (Herr, 2002).
(Herr, 2002) According to C.R.Bilardi in his book, The Red Church: or the Art of Pennsylvania German Braucherei (2009), two well known examples of these letters are the Koenigsberg Fire Brief of 1714 and the Magdeburg Himmelsbrief of 1783.