Rings are not solid objects and they consist of a large amount of small solid particles, or moonlets embedded in them. The larger the distance from the planet is, the smaller the orbital speed is.
The composition of the solid particles embedded in rings is water ice and the observation was based on their reflectivity that was measured and determined using infrared. The measurements determined that the dimensions of diameters of these particles can vary from millimeters to tens of meters.
Rings are formed when distance between a moon and a planet become so small such that the internal forces of the moon are overpassed by the planet's gravity and the moon is fragmented in pieces that are diffused in the form of a ring. The value of the critical distance between the moon and the planet is known as Roche limit. If the densities of moon and planet are alike, then the critical distance is near 2 times the planet's radius. Roche limit does not apply to small moons, whose gravities do not represent the binding forces, but the interatomic forces.