All the Jovian worlds have ring systems due to the massive tidal forces associated with the gas giants. The broken pieces are distributed into a ring shape. We know that that the rings are not solid or liquid since Doppler measurements show that the rings are made of separate particles moving in circular orbits. The brightness of the rings is proportional to the size of the particles in the rings. The faintest rings are made of icy dust.
Rings are very thin compared to their width.
Most are only a few tens of meters to a kilometer in thickness. This is due to the fact that a particle that lies in an orbit above and below the ring must pass through the ring twice each orbit. This leads to collisions which cause the particles to exchange energy and adopt velocities and directions similar to the particles in the rings. Saturn's rings are the most prominent and were show by Voyager to be composed of hundreds of ringlets. Gaps in the rings are due to orbital resonances with the outer moons.