The Rosetta Stone is an Ancient Egyptian artifact which was instrumental in advancing modern understanding of hieroglyphic writing. The stone is a Ptolemaic era stele with carved text. The text is made up of three translations of a single passage, written in two Egyptian language scripts (hieroglyphic and Demotic), and in classical Greek. It was created in 196 BC, discovered by the French in 1799 at Rosetta, a harbor on the Mediterranean coast in Egypt, and contributed greatly to the decipherment of the principles of hieroglyphic writing in 1822 by the French scholar Jean-François Champollion. Comparative translation of the stone assisted in understanding many previously undecipherable examples of hieroglyphic writing. The text of the Rosetta Stone is a decree from Ptolemy V, describing the repealing of various taxes and instructions to erect statues in temples.

After Napoleon's 1798 conquest of Egypt, the French founded Institut de l'Égypte in Cairo, bringing 167 scientists and archaeologists to the region. French Army engineer Captain Pierre-François Bouchard discovered the stone sometime in mid-July 1799, while guiding construction work at Fort Julien near the Egyptian port city of Rosetta (now Rashid). After Napoleon returned to France in 1799, the 167 scholars remained behind with French troops which held off British and Ottoman attacks. In March 1801, the British landed on Aboukir Bay and the French scholars carried the Stone from Cairo to Alexandria alongside the troops of de Menou. French troops in Cairo capitulated on June 22, and in Alexandria on August 30. The British claimed all of the archelogical materials as the property of the British Crown, including the Rosetta Stone. On March 11, 1802 it was presented to the Society of Antiquaries of London. Later it was taken to the British Museum, where it remains. White painted inscriptions on the artifact state "Captured in Egypt by the British Army in 1801" on the left side and "Presented by King George III" on the right.

Source: Wikipedia.

http://en.wikipedia.org/wiki/Rosetta_stone