Durin's Folk
Durin's Folk, also called the Longbeards, were the most renowned of the seven kindreds of the Dwarves, descended from Durin the Deathless, eldest of the Seven Fathers of the Dwarves. Their long history included the founding of Khazad-dûm and the kingdom under Erebor, and their kings played a great part in the affairs of Middle-earth.
Durin the Deathless
Durin was the eldest of the Seven Fathers made by the Vala Aulë, and he awoke alone in the Elder Days. He founded the great realm of Khazad-dûm (Moria) beneath the Misty Mountains, the grandest and longest-lasting of all Dwarf-kingdoms. So revered was he that his folk held that he was reborn again and again through the ages in his descendants, and several later kings bore the name Durin.
Khazad-dûm
For long ages Durin's Folk dwelt in Moria, growing rich and skilled, especially in the mining of mithril, the precious silver metal found nowhere else in such measure. The realm fell when the Dwarves delved too deep and roused a Balrog, Durin's Bane, which slew King Durin VI and drove the Dwarves out. Thereafter Moria stood empty and dreaded.
Wanderings and Erebor
Exiled from Moria, Durin's Folk wandered, founding new realms in the Grey Mountains and later under the Lonely Mountain, Erebor. Erebor too was lost, for a time, to the dragon Smaug, until Thorin Oakenshield, an heir of the line of Durin, reclaimed it in the quest told in The Hobbit. Notable members of the kindred included Balin, Glóin, and Glóin's son Gimli, who joined the Fellowship of the Ring.
Wars of the Third Age
Durin's Folk fought the long War of the Dwarves and Orcs, culminating in the great Battle of Azanulbizar before the East-gate of Moria. They also held firm in the North during the War of the Ring, defending Erebor and Dale against Sauron's allies.