Suitably modified versions of the Langevin equation introduced in Chap. 2 will be taken as a general basis for analytical explanations of macromolecular-chain motions. The reader will straightforwardly be led from the dynamics of freely draining polymer chains as the simplest case to entangled-chain phenomena and finally to mesoscopic confinement effects. The Langevin equation-based treatments will be supplemented step by step by additional force terms specific for the diverse model scenarios. The restriction to this equation-of-motion strategy is expected to favor the comprehensibility of this demanding field. The relaxation-mode solutions will be expressed in the form of predictions for diverse experimental techniques outlined in Chap. 3. This in particular refers to spin-lattice relaxation, coherent and incoherent neutron scattering, and mechanical relaxation.