Betazed is a major member of the United Federation of Planets. It is home to the Betazoid race.
Almost nothing is known about the political structure of Betazed. Betazed's ambassador to the Federation council, Lwaxana Troi, carries a number of ritualistic titles: Daughter of the Fifth House, Holder of the Sacred Chalice of Rixx, and Heir to the Holy Rings of Betazed. What, if any, meaning these titles have in Betazoid politics is unknown.
Betazoids are telepaths with varying levels of ability. They can send and receive thoughts with little effort, even extracting secret information in seconds, although a small number of races are resistant to their abilities.
Betazoids are physically almost indistinguishable from humans (the only visible difference being that Betazoids have black irises in their eyes), and they can interbreed, producing children who generally have less psionic ability, showing empathy instead of telepathy.
Betazed is not known to have any colonies in other star systems.
Betazed has no known military assets, relying entirely upon Starfleet for defense. They apparently don't even have an independent starship for their ambassador to use when travelling on official business.
Betazoid advisors are potentially useful in military organizations, since powerful telepaths can read the minds of enemy commanders at a considerable distance.