Short answers, pulled from the story.
Fenrir is a monstrous wolf in Norse mythology, the son of the trickster god Loki and the female giant Angrboða. He is foretold to kill Odin, the chief of the gods, during Ragnarok. His siblings are Hel and the world-serpent Jörmungandr.
The gods refused to kill Fenrir because they would not defile their holy places and sanctuaries with his blood, even though prophecies said he would cause their destruction. They chose to bind him instead, placing him on the island of Lyngvi on the lake Amsvartnir.
Gleipnir was a fetter made by dwarves in Svartálfaheimr, commissioned by Odin's messenger Skírnir after two earlier iron chains failed to hold the wolf. It was crafted from six mythical ingredients and felt smooth and soft as a silken ribbon, yet it grew stronger the more Fenrir struggled against it.
Fenrir refused to allow Gleipnir to be placed on him unless one of the gods put a hand in his mouth as a pledge of good faith. Only Týr agreed, extending his right hand into the wolf's jaws. When the Aesir refused to release Fenrir after he was bound, the wolf bit off Týr's hand at the wrist, the joint the source calls the wolf-joint.
At Ragnarok, Fenrir swallows Odin, killing him. Odin's son Víðarr then kills Fenrir by driving a foot into his lower jaw and tearing his mouth apart with one hand. Víðarr wears a legendary shoe assembled from material collected throughout all time for this act.
Fenrir is identified on several runestones: Thorwald's Cross on the Isle of Man, dated to around 940, shows what scholars read as Odin being consumed by the wolf. The mid-11th century Gosforth Cross in Cumbria, England, depicts what has been interpreted as Víðarr killing Fenrir. The 11th century Ledberg stone in Sweden may also show Odin at the moment of his death.