What composes planetary rings?
Planetary rings, depending on the planet we're talking about, are composed of pieces of rock and ice - this could be water-ice (as in the case of Saturn)
To understand how rings are formed, let's first look at our moon. Earth is pulling at the moon by gravity forces. But the pull on the near side is greater than the pull on the back side (because that is farther away). This creates tidal forces that 'try' to pull the moon apart, and only the gravity within the moon itself keeps it together.
If the moon were much closer the realtive difference between the pull on the front and the back would be much greater, en the moon would be pulled apart.
The other way around: if chunks of rock and ice are too close to a planet, they would never get the chance to gravitate together to form a 'moon' because of this. So all the debris stays in orbit at different distances, and with different speeds.
And they all tend to collect right above the equator of the planet.