In this chapter we describe the equations of motion associated to a Solar sail, which we assume it is subject to different forces: the pressure exerted on the sail by Solar radiation and the gravitational attraction of two primaries, e.g. Sun and Earth, moving on circular orbits around their common barycenter. We describe the dynamical behavior as the orientation angles of the sail are varied, leading to the analysis of conservative and dissipative systems, according to the choice of the parameters. We also discuss the energy preservation in different cases.