Gollum's Biography
Spoiler Below
Gollum led Sam and Frodo down the tunnel of Cirith Ungol, outside Mordor. There, he awakened the giant spider Shelob who had remained dormant for years, as an act of revenge. In a struggle with Sam, Gollum fled down one of the tunnels. After Frodo being captured, Shelob injured and Sam saving Frodo from the tower of Barad-dur, Frodo and Sam continued their journey to Mount Doom, with Gollum still following them behind. Sam and Frodo reached Mount Doom and began to climb. When sam reached the door to the inner mountain, he could no longer resist the Ring's power, for it had become stronger and stronger, the closer they got to Mount Doom. Frodo had just claimed the Ring for his when Gollum pounced out from behind the rocks and fought with the invisible Frodo. He cut of Frodo's finger that bore the ring and in his jumping of triumph, he lost his balance and toppled into the fiery, molten depths of the mountain, taking and destroying the Ring with him. As evil as Gollum might be, it was just as well that he stole the Ring from Frodo in Mount Doom, because he helped Frodo to fulfill his quest in destroying the Ring and helped Frodo save Middle-Earth - something he couldn't have done at this point. As Gandalf said earlier in The Fellowship of the Ring, Gollum has yet a part to play in Frodo's quest to destroy the Ring.
He tracked the ring down and found that it's bearer was now Frodo Baggins, Bilbo's nephew. He followed the Fellowship into the caves of Moria. And after the breaking of the Fellowship, he followed Sam and Frodo to Emyn Muil. After attacking Frodo and Sam while they were sleeping, he was tied up and made a deal with Frodo that he would take them to Mordor if they would untie him. So Gollum lead Frodo and Sam to the very mountain ranges surrounding Mordor. After turning back, because he knew of a safer way - a tunnel, Frodo agreed to be led this way and rather reluctantly by Sam, who didn't trust Gollum. On their way, they were captured by Farimir, the son of the steward of Gondor and his men, which delayed them for a few days. Gollum felt that Frodo had led him to be captured and felt betrayed. Farimir agreed to let Sam, Frodo and Gollum go. Gollum continued to lead Frodo and Sam to the tunnel.
Gollum is the creature that we catch a glimpse of in The Fellowship of the Ring in the caves of Moria. He was named Gollum because of the noise he made 'Gollum' when he coughed. He plays a much bigger part in The Two Towers where he joins Sam and Frodo on their journey to Mordor. He is a skinny, but strong creature, who will do anything to get hold of the Ring of Power. But Gollum wasn't always like this. He was once a hobbit named Smeagol. Smeagol had a normal and happy life that any hobbit had. After the ring of power betrayed Isildur, Smeagol's cousin Deagol, 2,500 years later found the ring at the bottom of a lake. Drawn to it's power Smeagol eventually killed Deagol to steal the ring. He was banished into the caves of the misty mountains where the ring devoured him. The Ring gave him long life for 500 years. Over this time he became overly obsessed with the ring and it destroyed him. So when the ring abandoned Gollum and was picked up by Bilbo Baggins, Gollum set out to find it. He was captured by the servants of the Dark Lord and was tortured in Mordor till he revealed the location and the bearer of the One Ring. Then he was released.