Padan Aram in the Old Testament
Padan Aram is "the flat land of Aram," contrasted with the more mountainous region of the N. and N.E. of Mesopotamia (Hos. 12:12), "the field (sedeh) of Aram" (Gen. 25:20), the same as Aram Naharaim, "Aram of the two rivers," or Mesopotamia (Gen. 24:10). Aram expresses the highland of Syria, contrasted with the lowland of Canaan. The land between Tigris and Euphrates is a vast flat, except where the Sinjar range intersects it. The home of Rebekah, Laban, etc.
International Standard Bible Encyclopedia, which is in the public domain (with minor edits).