Short answers, pulled from the story.
Sól is the personification of the sun in Norse and broader Germanic mythology, described as a goddess who drives a horse-drawn chariot across the sky. She is the daughter of Mundilfari and the sister of Máni, the personified moon, and in the Prose Edda she is also named as the wife of a man called Glenr.
During Ragnarök, the wolf Sköll, who has pursued Sól across the sky throughout all of time, will finally catch and kill her. Before this happens, she will give birth to a daughter who will continue riding her mother's path through the heavens after Ragnarök's events are complete.
The Trundholm sun chariot is a Nordic Bronze Age artifact depicting the sun being drawn across the sky by a horse, a motif that directly parallels the mythological description of Sól's journey. Rudolf Simek identifies it as evidence that Bronze Age Scandinavians already viewed the sun as a life-giving heavenly body, and the image of horses pulling the sun survived into the medieval Edda texts.
She is called Sól in Old Norse, Sunna in Old High German (also used as an Old Norse and Icelandic synonym), and a cognate form in Gothic. The Poetic Edda poem Alvíssmál lists additional names: the dwarf Alvíss says she is called sól by mankind, sunna by the gods, Dvalinn's deluder by the dwarfs, everglow by the jötnar, lovely wheel by the elves, and all-shining by the sons of the Æsir.
One of the two Old High German Merseburg Incantations, dated to the 9th or 10th century, names Sunna as the sister of a figure called Sinthgunt. Both Sinthgunt and Sunna are described as singing healing charms over a foal that sprained its foot, alongside Friia, Volla, and Wodan.
The wolf Sköll pursues Sól, described in Grímnismál as the bright bride of the heavens. A second wolf, Hati Hróðvitnisson, runs ahead of Sól to chase her brother Máni. The Prose Edda states that Sköll will eventually catch Sól during Ragnarök.