Centaur type cometary bodies are passive bodies found in the cold, outer parts of the solar system, beyond the ice line but within the kuiper belt. They tend to drift in similar orbits to outer planets, making them likely to have their orbits shifted and either sent plummeting into the inner system, or jettisoned out into galactic space.
Centaurs are relatively untouched since their formation, though will have been affected by their star's radiation more so than other passive cometary class bodies.
They will consist mostly of ices, with some organic tholins and maybe traces of silicates.
They are less common than Kuiper or Oort bodies, but due to inhabiting a considerably smaller volume of space, and often much easier to find and reach, and so may be heavily colonised, or at least mined, in systems with a high level of space capability.