He was one of the Titans, son of the Titan Iapetos and, depending on which version you read, his mother was the Goddess Themis or Clymene. He married Hesione and was the father of Deucalion, though the mother of this child, depending on the version, was either Hesione or Pronoea.

The story reads that the Gods defeated the Titans, and were deciding how man should honor the Gods. Prometheus was chosen to decide how sacrificial victims were to be offered to the Gods. Prometheus had cut up an ox into two parts, one was the choice cuts wrapped in the stomach, to make its look like the unwanted parts, and the unwanted parts were covered with fat to make them look like the good parts.  Zeus discovered the trick and took fire away from man as punishment.

Prometheus turned around and stole fire from the Gods and gave it back to man. Zeus then created Pandora (from clay), giving her a dowry in a jar (it was a jar as translated from the Greek, not a box).  Prometheus' brother Atlas Epimetheus (which translates to Atlas Afterthought) was taken by her beauty, and married her, even though he was warned by his brother about Zeus' trickery, and when she opened her dowry the evils and diseases came out of the jar. She closed the lid, but only Hope remained.

Of course, Zeus was not happy with just this, he went and punished Prometheus by chaining him to a pillar where either an eagle or vulture came each day and ate his liver. The liver grew back each night to be eaten the next day.

There are some variations, depending on the translations. In one variation, Prometheus was the creator of mankind. The plays, and books and stories that come after the original Greek start to change the story rapidly, and, of course, Hollywood totally changed everything around. I prefer the original Greek text translations.