This document discusses natural satellites in the solar system. It begins by explaining that most planets have moons that orbit around them, similar to Earth's moon. It then defines natural and artificial satellites, noting that natural satellites cannot have their trajectories artificially modified. The document provides data on the number of moons orbiting each major planet. It describes how planetary moons can vary in shape and size, and notes some theories for how moons may have originated. In general, observation of moons requires powerful instruments as most are not visible to the naked eye like Earth's moon.