This review will focus on the use of the dynamics of observed comets to provide clues to the properties of the cometary reservoirs from which they come. The properties of the reservoirs can in turn be used as clues to planetary formation processes in the outer solar system. Particular attention will be paid to the Trans-Neptunian scattered disk (SD). It will be shown that the observed properties of the SD are consistent with those predicted for the remnants of a population of planetesimals scattered by Neptune during outer planet formation in the early solar system. Such an SD will be shown to be the plausible source not only of Jupiter Family comets and Centaurs, but also of Halley-type comets (which were previously thought to originate in the Oort cloud). Recent simulations of the dynamical clearing of planetesimals to form the Oort cloud will also be reviewed, as will the challenges faced in understanding the properties of the Oort cloud.