Uranus and Neptune also have strong magnetic fields, but their centers are offset from the planets' centers, and they are tipped away from the planets' rotation axes. Perhaps they are telling us something about the boundary between the core of the planet and the surrounding layers, but it's hard to understand what's really causing these fields. All of these are big, some have atmospheres. Io is the most volcanically active place in the solar system. Ganymede is bigger than Mercury.
Titan has a thicker atmosphere than the Earth, and Triton orbits Neptune the wrong way.
Your textbook includes many more details about the mid-size and smaller satellites an the ring systems. We discussed these only briefly, but you should know what useful things they can tell us about the outer solar system. The ring systems are all close to the planet, where tides would either rip a moon apart or not let a moon form. Perhaps Neptune will have spectacular rings some day in the future when Triton strays to close to the planet.