The Rosetta Stone is one of the most famous objects in the British Museum. The Stone is a broken part of a bigger stone slab. It has a message carved into it, written in three types of writing. It was an important clue that helped experts learn to read Egyptian hieroglyphs (a writing system that used pictures as signs). The writing on the Stone is an official message, called a decree, about the king (Ptolemy V, r. 204–181 BC). The decree was copied onto large stone slabs called stelae, which were put in every temple in Egypt. It says that the priests of a temple in Memphis (in Egypt) supported the king. The Rosetta Stone is one of these copies, so not particularly important in its own right.

Source: British Museum