Gil -Galad, the only son of the High King of Fingon, was born in Beriland late in the First Age, and was still a child at the time of the Dagor Bagollach.  His father sent him to Cirdan at the Havens for safekeepings when Morgorth broke the Seige of Angband in the battle. 

Fingon was lost in the Nirath Arnoe and died, but the crown passed to Gil-galad's Uncle Turgon in Gondolin, rather than Gil-galad himself (presumeably because of his youth at that time).  When the city of Gondolin was defeated, Gil-galad received the Kingship of Noldor.  He dwelt with the Exiles of the city at the Mouth of Sinon during the remainder of the First Age.  

After the destruction of Beriland during the War of the Wrath, Gil-galad founded a kingdom in Lindon in the far northwest Middle-Earth, between the Blue Mountains and the Great Sea.  There, he and his people prospered, until Sauron returned.  He came first to Lindon in the form of Annatar, the Lord of Gifts, but Gil-Galad and Elrond rejected him.  Soon after, the One Ring was forged, and there was war in Middle-Earth between the Elves and Sauron. 

After the Downfall of Númenor and the establishment by the Elendili of the Dúnadan kingdoms in exile, there was peace in Middle-Earth.  For a time it was believed that Sauron had been destroyed in the fall of Númenor but this not the case.  Sauron began a war against Gondor, which was closest to Mordor. 

Gil-Galad then formed the Last Alliance of Men and Elves with Elendil, High King of the Dúnadain-in-Exile.  The armies of Elves and Men, victorious after the Battle of Dagorlad, laid siege to Sauron in Mordor.  At the end of the siege, both Gil-Galad and Elendil were slain by Sauron himself when he came out of Barad-Dúr and did battle. Gil-Galad died from the heat of Sauron's body.