Clay tablets were a medium used for writing. They were common in the Fertile Crescent, from about the 5th millennium BC. A clay tablet is a more or less flat surface made of clay. Using a stylus, symbols were pressed into the soft clay. It is possible to correct errors on the tablet. The tablet was then baked or left in the sun until dry and hard.
Cuneiform was the first writing used on clay tablets. The system was used by several civilisaations who spoke several different languages.