The Vorta were once small timid ape-like creatures that lived in hollowed out trees and living in fear of the many predators that would hunt them for food. One day a Changeling happened upon a Vorta family while it was running from an angry mob who was trying to kill it. The Vorta family took the changeling in and hid it from the mob, saving its life and earning its gratitude. In response for their kindness towards a Changeling, something the founders rarely, if ever, experience from solid life-forms, the Changeling promised them a position of power within the Dominion.
The Vorta, thanks to the genetic modifications made by the founders, have excellent hearing, though they have no appreciation for art and have poor eyesight. They also have a limited sense of taste; they cannot taste anything beyond the nuts, fruits and berries of their home world - which is seen by Vorta as a reminder of where they came from and what they owe the Founders. Vorta are also immune to most forms of poison, something which Weyoun once remarked was a useful ability for a diplomat.
Each Vorta is in charge of distributing a drug known as Ketracel-white among the Jem'Hadar under their command, the event is somewhat of a ritual with the Jem'Hadar pledging their loyalty to the founders before receiving their vials of the drug.
Some Vorta possess telekinetic abilities, and are able to generate telekinetic blasts of energy that can knock out humans and disable energy barriers.
The Vorta care little for the Jem'Hadar under their command, seeing them as no more than tools to get a job done and will quite happily sacrifice them all in order to prolong their own survival.
The Vorta are cloned by the founders, when one dies, they are replaced by their copy, offering them a kind of immortality. On occasion, a clone is "defective" and does not behave like a typical Vorta, the reason for this is unknown, but any defective Vorta are killed without question.
The Vorta are 'built' with a self termination device in their brain stem, this is in case a Vorta is captured, though they are ordered to use it if they turn out to be defective. They are made to believe that the process is painless, but that isn't the case.
The Vorta are incapable of dreaming. Though defective Vorta are able to dream.