Short answers, pulled from the story.
The Greek name Phoibē means pure, bright, and radiant. Ancient lexicons define this word as an epithet given to Apollo when he appears as a sun-god. The same root also describes clear or pure water in ancient texts.
Phoebe was one of the twelve divine children born to Uranus and Gaia. These Titans ruled before the Olympian gods took power over the cosmos. Hesiod recorded these family connections in his work called Theogony.
A speech by Aeschylus places Phoebe at the center of the Delphic oracle's history where she receives control from her sister Themis. Phoebe then passed the gift to her grandson Apollo as a birthday present. This transfer of power remains a key element in ancient literary accounts of the sanctuary.
Roman poets frequently equated Phoebe with Diana and Luna while maintaining distinctions. Servius wrote that Phoebe is Luna just as Phoebus is Sol. The identity shift occurred primarily through Roman poetic tradition rather than Greek worship practices.
Phoebe appears on the southeast corner of the Pergamon Altar fighting against Giants. She wears a diadem and a very creased dress while wielding a flaming torch. No distinct iconography exists for her outside this specific monument.