The observation of gravitational wave signals from inspiralling andcoalescing binary black holes has been significantly helped, from the theoreti-cal side, by the availability of analytical results on the motion and gravitatio-nal radiation of binary systems, and notably the Effective One-Body (EOB)theory of the motion and radiation of binary systems. We shall review thestructure of perturbative calculations in classical gravity from various pointsof view : post- Minkowskian, post-Newtonian, self-force, reduced action, ef-fective one-body. We shall also discuss the (two-way) maps between classicaldynamics and quantum scattering amplitudes.