Short answers, pulled from the story.
Perseus, a Greek hero, killed Medusa by beheading her while looking only at her reflection in a mirrored shield given to him by Athena. He was sent on the errand by King Polydectes of Seriphus, who wanted Perseus's mother for his wife.
According to Hesiod and Apollodorus, Medusa's parents were the sea-god Phorcys and his sister Ceto. Her sisters were Stheno and Euryale; together the three were known as the Gorgons. Medusa was the only mortal among the three.
When Perseus beheaded Medusa, two beings sprang from her body: Pegasus, a winged horse, and Chrysaor, a giant wielding a golden sword. Medusa had been pregnant by Poseidon at the time of her death.
The Gorgoneion was an evil-averting device in classical antiquity, depicting the head of Medusa. It appeared on shields, breastplates, and temple architecture across the ancient world. Scholar Jane Ellen Harrison argued it originated as a ritual mask, with the myth of the living Medusa invented later to explain it.
The Roman poet Ovid presented Medusa as originally a beautiful maiden whose hair was transformed into snakes after Neptune mated with her in the temple of Minerva, and Minerva punished her for the transgression. Earlier Greek sources did not include this origin, though ancient depictions of a beautiful Medusa predate Ovid.
Feminist writers and artists began reclaiming Medusa from the mid-1970s onward as a symbol of female rage and protective power. A cover of Women: A Journal of Liberation in 1978 featured Medusa's image with an explanation that it could guide women "through the depths of our anger into the sources of our power." Hélène Cixous's essay "The Laugh of the Medusa" argued that patriarchal retellings had turned a figure of female desire into a monster.