Who is Maeglin from The Silmarillion and what is their importance?

Maeglin is the son of Eol and Aredhel, making him Turgon's nephew. He is born in Nan Elmoth and yearns as a child to see Gondolin and the sons of Feanor. Aredhel and Maeglin go to Gondolin while Eol is at the feast of the Dwarves. In Gondolin, both of his parents die, and Turgon honors Maeglin. Maeglin loves Idril but cannot marry her because she is his first cousin. He betrays Gondolin to Morgoth after Tuor marries Idril. Maeglin means Sharp Glance, and his mother also gives him the name Lemion or Son of Twilight, a Quenya name.