The Edo were a humanoid species from the planet Rubicun III. They outwardly resembled Humans of Caucasian descent. Most members of the species had blonde hair, though brown hair was also a possibility.
The Edo were a free-spirited people, extremely welcoming and friendly and very open sexually with themselves and visitors. Edo women greeted men with a deep embrace, and offered themselves sexually to any man who would accept them; Edo men behaved in the same fashion with women. It was customary among the Edo to run from place to place instead of walking. Their society was peaceful and extremely law-abiding. Criminality had been largely eliminated in the distant past and was virtually unknown by 2364.
The unique tranquility of the Edo had a price, however. Criminal punishment was only enforced in random punishment zones that only the planet's Mediators knew, but anyone who committed any crime in the punishment zone faced a quick execution with a poisoned syringe.
The Edo were protected by a trans-dimensional super-entity in orbit around their planet, which they worshiped as "God".
The Edo spent time with music, dancing, massages, kissing, and playing games with die or balls.
There was limited variation in Edo clothing, with most members of the species wearing the same type of costumes. However, only the leaders and the mediators wore necklaces including the Edo symbol. The mediators wore a grey and black costume that identified their responsibilities. Edo boys went about shirtless, but girls and adults of both sexes wore tops. (TNG: "Justice")
Later in 2364, during an investigation of the USS Enterprise-D crew, Lieutenant Commander Dexter Remmick interrogated Captain Jean-Luc Picard about him having violated the Prime Directive and interfered with Edo laws to save Wesley Crusher, son of Doctor Beverly Crusher. (TNG: "Coming of Age")
In 2380, Ensign Beckett Mariner suspected Lieutenant Barbara Brinson of potentially being a member of the Edo when she became Brad Boimler's girlfriend, describing them as "one of those sexy people in rompers that murders you just for going on the grass!" (LD: "Cupid's Errant Arrow")
The Edo's clothing was designed by Costume Designer William Ware Theiss. While working on Star Trek: The Original Series, he had created many likewise precariously draped, sexually suggestive costumes, becoming renowned for doing so. Although his newer designs for The Next Generation were more subdued than his earlier original series work, the Edo's focus on health and sex provided him with a logical story reason for him to return to his signature draped costume style. (Star Trek: The Next Generation - The Continuing Mission, p. 55)