The Dwemer, or dwarves, are a former race of humanoids mentioned in the lore of The Elder Scrolls. They mysteriously went extinct, and only one, Yagrum Bagarn, has yet appeared alive in any of the games.
The Dwemer were classified as Mer, and thus were related to other humanoid races such as the Dunmer (Dark Elves) and Altmer (High Elves). However, they were commonly called dwarves, and resembled the conventional dwarves in other fantasy universes.
The Dwemer were natives of the Morrowind region, mainly inhabiting Red Mountain initially but later spreading across Tamriel. They were a reclusive and industrious people, who shunned religion and valued technological innovation and secular philosophy. This led them to much conflict with Morrowind's religious Chimer race until, at the height of a war between the Dwemer and a Chimer alliance led by Nerevar, every Dwemer in Tamriel spontaneously disappeared. It remains a mystery to Tamrielic historians how and why this occurred, but the event is mostly attributed to the Dwemer's meddling with the Heart of Lorkhan, an extremely powerful object said to be the heart of a god.
The only Dwemer remaining in existence after this was Yagrum Bagarn, who happened to be in Akavir at the time instead of in Tamriel. Bagarn appears in The Elder Scrolls III: Morrowind and can share his knowledge about the Dwemer's fate with the player.
Despite the Dwemer's extinction, their legacy is still apparent in the many elaborate ruins they left behind, particularly in Vvardenfell. The player can often find valuable Dwemer artifacts in these ruins, including armor and weapons. Caution is required, though, as most are guarded by hostile ghosts and ancient Dwemer-built robots called Centurions, or by groups of criminals who use the ruins as hideouts.