Haliians were a species. Externally, they were distinguished by the fact that their foreheads have a slight bulge above each eyebrow. They also had a distinctive crevice between the brows, on the bridge of the nose.
The Haliians were a telepathic species, although they were limited to person to person empathy. A special crystal called a Canar, when held by an Haliian, has the potential to greatly increase their telepathic abilities and allow them to "bond" with others and share their thoughts. One of their holidays was the Batarael, at which a traditional song called the Horath was sung. (TNG: "Aquiel")