Short answers, pulled from the story.
Leda was named as the mother of four famous children: Helen of Troy, Clytemnestra, and the twins Castor and Pollux. Helen and Pollux were children of Zeus, while Clytemnestra and Castor were children of her husband King Tyndareus of Sparta.
Zeus disguised himself as an injured swan to avoid alerting his wife Hera. He pretended to be fleeing from an eagle, which gave him a pretext to fall into Leda's lap. According to Hyginus, this event took place near the river Eurotas.
Castor was the son of the mortal King Tyndareus of Sparta, while his twin Pollux was the son of the god Zeus. Leda lay with both Tyndareus and Zeus on the same night, resulting in the twins having different fathers and different natures.
Leda has been depicted by Leonardo da Vinci, Michelangelo, Raphael, Peter Paul Rubens, Salvador Dali, Cy Twombly, and Edouard Houssin, among others. Australian artist Sidney Nolan produced at least a dozen interpretations of the subject during the 1950s and 1960s.
In one version, the goddess Nemesis, not Leda, was impregnated by Zeus in the form of a swan and laid an egg. A shepherd found the egg and gave it to Leda, who kept it in a chest until it hatched and Helen was born. Zeus then created the constellation Cygnus to commemorate Helen's birth.
In October 2022, Hozier wrote Swan Upon Leda in response to the US Supreme Court's Dobbs v. Jackson decision, which repealed Roe v. Wade. Eli Goldstone's 2017 novel Strange Heart Beating also draws on the myth and takes its title from William Butler Yeats' poem Leda and the Swan.