Pandora was the very first woman, formed out of clay by the gods. The Titan Prometheus had originally been assigned with the task of creating man. He stole the secret fire in a giant fennel-stalk and restored it to mankind. Zeus was angered, and commanded Hephaistos and the other gods to create a woman, Pandora, and endow her with the beauty and cunning. He then delivered her to Epimetheus, the foolish younger brother of Prometheus, for a bride. When he had received her into his house, Pandora opened the pithos which Zeus had given her as a wedding present, and released the swarm of evil spirits trapped within. They would ever afterwards plague mankind. Only Elpis (Hope) remained behind, a single blessing to succor mankind in their suffering.
So the box is actually a jar. Stupid mortals ;)