According to NASA, scientists have many theories about Saturn's rings, but there is no proven explanation for the rings. The rings are made of debris trapped in the gravitational pull of Saturn, and there are multiple theories as to where this debris originated.
One commonly held theory states that the rings are the result of an accumulation of dust, ice and other particles trapped in the gravitational pull of Saturn. Because of its size, Saturn has a large gravitational pull and may have attracted debris from space into orbit, forming the its rings around the planet. Some of the debris are tiny particles of dust, while other debris are as big as a truck or building. Saturn also has at least 62 moons, which may have been drawn to the planet in a similar manner.
Another theory on the creation of Saturn's rings indicates that asteroids impacting the planet's many moons created large quantities of debris. As with the dust collection theory, gravity trapped the impact debris, which formed an orbit around the planet in the form of the rings.
A third theory believes that Saturn itself formed through the accumulation of debris as other moons collapsed. During its formation, Saturn could not absorb all the fragmented material, so the debris ended up orbiting the planet as a ring system.