The Vorta are a humanoid species originating in the Gamma Quadrant. They were genetically engineered by the Founders to act in administrative, scientific and diplomatic capacities within the Dominion. The Vorta are also primarily charged with overseeing the Jem'Hadar soldiers, and the distribution of Ketracel-white.
This means that most Vorta do not view death as most humanoid species do and faced it with arrogance. They were also equipped with a "kill switch" that they could trigger to commit suicide. This was mainly a system to stop important Vorta from falling into the hands of the Founders enemies. Most Vorta when faced with capture would kill themselves knowing that a new clone would soon be released to continue their service to their gods. (DS9: "Treachery, Faith and the Great River")
Both before and during the Dominion War, the crew of Deep Space 9 had dealings with several Vorta. Most notable of these was Weyoun, who represented the Dominion during the period of Cardassian occupation in 2374. (DS9: "To the Death", "A Time to Stand", "Behind the Lines", "Treachery, Faith and the Great River", et. al)
When the morphogenic virus created by Section 31 killed nearly all the Founders in the late 2370s, the Jem'Hadar committed mass suicide, taking most of their Vorta overseers with them. Only a handful of Vorta survived, and most of the Dominion's cloning facilities were destroyed. (Star Trek: Pendragon: "Shadows of the Fire")
U'lanna cloning technology couldn't clone Vorta, while it was able to clone Jem'Hadar, resulting in their own versions of Jem'Hadar warships being entirely manned by Jem'Hadar. (Star Trek: The Stoneship Files: "Ancient Horrors")