Salarians, who possess one of the three permanent Citadel Council seats, are a species renowned for their mental acuity, technical skill and their high aptitude for espionage. Salarians have a very high metabolism rate, lowering their life expectancy to about 40 Earth years, but also necessitating very little sleep, around 1-2 hours per day.
In the interstellar community, they have created many of the major technological advances that now fill the galaxy. Highly intelligent, their mental acuity is galactically renowned. In fact, they are considered to be hyperactive by most other races; Salarians, however, disagree with this prognosis, considering other races to be slow and dim-witted.
They favor political liberalism, making them a counter-balance to the conservative Turians and centrist Asari on the Citadel Council. The Salarian Union is largely governed by a group of dynastic families ruled by female elders. Of the three permanent Council species, their economy is the smallest, but is still substantially larger than that of the human Systems Alliance. The Salarians were responsible for the elevation of the Krogan race to combat the invading Rachni, and they were subsequently responsible for creating the "Genophage" biological weapon used to quell the later Krogan Rebellions. Militarily, they are considerably weaker than the Turians in head-on combat, preferring to employ sabotage, reconnaissance, counter-intelligence and commando operations against any enemy. However, in unconventional warfare, the Salarians are perhaps second to none. They excel at information gathering and while they consider outright direct war to be a last resort, once they do engage in war, it's almost always by surprise (they see a declaration of war as strategically unsound) and by a strategically dominant force - after all, they've long since figured out what and who they are fighting against and how their foes are going to fight.
Salarians are not notably religious, but as free-willed sentients there are exceptions. One of the less-favored Salarian religions (which the Council deems a "cult") worships a goddess, and claims that a certain pattern of overlapping craters in the southern hemisphere of Trelyn resembles her. There has also been a small movement towards a kind of "wheel of life" form of pantheistic reincarnation that has taken root to a limited extent among Salarians.
In the novel Mass Effect: Ascension, a "Salarian Lystheni offshoot" is mentioned. It can be speculated that the Lystheni are a criminal organization similar to the racist, human organization Cerberus as the novel describes them as "those unwelcome in Citadel space", it could also be speculated that they are a Salarian subspecies.