Pharaoh Narmer (aka Menes -- likely a legendary king) is shown on two sides of the palette wearing different crowns, the hedjet or white crown of Upper Egypt on the obverse and the deshret or red crown of Lower Egypt (basically, the delta area of the north) on the reverse. It may represent an historical event - the unification of Egypt by the pharaoh, but its historicity is debated. The king is represented as larger than other figures, especially on the obverse, where he holds the mace, a symbol of power. There are bovine horns at the top thought to represent the goddess Hathor.
The Narmer Palette is thought to date from about 3150 B.C.
British archeologist James E. Quibell found the Narmer Palette in his 1897-1898 excavations at Hierakonpolis in the foundations of a temple. Hierakonpolis is an ancient urban area of Egypt thought to date back to the neolithic archaeological eras of either Naqada I or late Badarian.
Source: Steve Vinson "Narmer" The Oxford Encyclopedia of Ancient Egypt. Ed. Donald B. Redford, Oxford University Press, Inc., 2001.
For information on the iconography of the Narmer Palette, see "What a King Is This: Narmer and the Concept of the Ruler," by Toby A. H. Wilkinson. The Journal of Egyptian Archaeology, Vol. 86, (2000), pp. 23-32.
