"Middle Egyptian" is the name of the court language spoken during the Middle kingdom (2000-1700BC). It survived as a written language until the very end of the Ancient Egyptian civilization, being considered as a "classical language" by the egyptian themselves, the same way as latin and classical arabic have (and in the case of the second, still is) been used in certain contexts, due to their prestige and sacred status.
Most of the texts written in hieroglyphs pretended to be Middle Egyptian.
the illustration is the hieroglyph of the owl , which simply writes the consonnant m. It comes from the white chapel of Sesostris in Karnak. (photo by J. F. Rosmorduc).