The name of a great Lord of Rivendell means "a star dome" in Sindarin. He was born in FA 543 to Earendil and Elwing the White. Elros, the first King of Numenor, was his brother.
Elrond is one of few characters of "The Lord of the Rings" who lived in three epochs. He was one of the wisest and most powerful elven lords. This is how Tolkien described him: "The face of Elrond was ageless, neither old nor young, though in it was written the memory of many things both glad and sorrowful. His hair was dark as the shadows of twilight, and upon it was set a circlet of silver; his eyes were grey as a clear evening, and in them was a light like the light of stars. Venerable he seemed as a king crowned with many winters, and yet hale as a tried warrior in the fulness of his strength. He was the Lord of Rivendell and mighty among both Elves and Men."
In SA 1695 Elrond fought against Sauron together with Gil-Galad, who was the last King of Noldor. In 1697 Elrond erected Imladris (or Rivendell), where the Elves and the Dunlendings found shelter throughout millenniums. In SA 3430-3441 Elrond marched as the Herald of Gil-Galad in the War of the Last Alliance. After the fall of Sauron, Elrond counselled Isildur to destroy the One Ring for good. But Isildur chose to keep the Ring.
In TA 109 Elrond married Celebrian, a daughter of Celeborn and Galadriel. In TA 130 two sons, Elladan and Elrohir, were born; and in TA 241 his daughter, Arwen, was born.
Gil-Galad entrusted Elrond one of the greatest of the Three Elven Rings - Vilya (which means "sky" in Quenya). Elrond was well-aware of the Rings of Power, of their potential and their history, and eagerly shared his knowledge at the Council. He advised to throw the Ring into the Cracks of Doom where it was forged; for it was the only right decision.
Elrond looked nobly and was a bit higher than Gandalf. He welcomed both courage of an old hobbit Bilbo, who volunteered to destroy the One Ring, and Sam's deep devotion to Frodo, who managed to make his way to a secret Council.
After the end of the War of the Ring Elrond left Middle-earth, leaving Rivendell to his sons. He arrived at the Grey Havens very kinglike: "Elrond wore a mantle of grey and had a star upon his forehead, and a silver harp was in his hand, and upon his finger was a ring of gold with a great blue stone, Vilya, mightiest of the Three."
Over the Sea Elrond found eternal life, for he had nothing more to do in Middle-earth - Sauron was destroyed, thus his mission was successfully fulfilled.