Short answers, pulled from the story.
Gimli is played by John Rhys-Davies, a Welsh actor. Rhys-Davies confirmed on the extended DVD of The Fellowship of the Ring that he deliberately chose a Scottish accent for the role, describing it as "an almost Glasgow Scottish accent" suited to the character's fierce belligerence.
Gimli asked for a single strand of Galadriel's golden hair as an heirloom for his house, but said he could not presume to ask for such a gift. Galadriel was so moved by his humility and boldness that she gave him three hairs instead of one. Scholars note she had refused the same request from Fëanor, one of the greatest of the Noldor, multiple times.
Dragon-sickness is described as a bewilderment or enchantment caused by a dragon's hoard that makes one so consumed by greed for gold that one would starve rather than give it up. Tolkien traced it to line 3052 of the Old English poem Beowulf. Galadriel's words to Gimli, that gold shall flow through his hands but have no dominion over him, make him the only Dwarf granted immunity to it.
Gimli killed 42 Orcs at Helm's Deep, beating Legolas by a single kill. The two engaged in a friendly slaying contest during the battle, with Legolas killing 41.
Gimli leads Dwarves south to Aglarond and becomes the first Lord of the Glittering Caves. He and his people construct great works in Rohan and Gondor, including replacing the ruined gate of Minas Tirith with one made of mithril and steel. After Aragorn's death, Gimli, then 262 years old, sails with Legolas into the Undying Lands, the first Dwarf ever to do so.
Gimli is the son of Glóin, who was a member of Thorin's company in The Hobbit. Gimli is also the third cousin once removed of Dáin II Ironfoot. He had wanted to join his father on the quest to reclaim Erebor but was considered too young at age 62.