Planetology is the study of other planets, those in our solar system and those beyond it. It is also referred to as planetary science. Given that what is currently known about any planet is overwhelmingly about Earth, the field of planetology is largely about comparative planetology: comparing what is known about Earth with what is being discovered about other planets.
Planetology draws on a multidisciplinary approach employing biology, chemistry, climatology, environmental science, geology, meteorology, and physics. To some extent it may also draw upon the social sciences (e.g. sociology and paleontology) in that the Earth has been influenced to some extent by the activities of humanity and this influence has made little or no impact on other planets.
Planetology studies the origin, history and possible future of planets, characteristics and nature of atmosphere, surface and internal geology, orbital path and gravitational influences. 
Essentially, planetology encompasses the same fields of geology. There is a heavy emphasis on surface formation including the cause and evolution of craters and flow dynamics of vulcanology. Technology encompasses multi-spectrum telescopy overall and robotic space craft in particular in the solar system.
Studies of the Earth which encompass measuring, modeling, and interpreting the configuration and motion of the crust, mantle, and the core are used to support theoretical work on other planets. Processes studied include erosion and impact crater formation, faulting, orbital evolution, rotational dynamics, tectonism, volcanism, mantle convection, core magnetohydrodynamics and, in some cases, post-glacial rebound. Planetologist use data describing patterns of geophysical stress and seismicity, gravity, magnetics, temporal variations in rotation and topography.