The book systematises the results of over 15 years of anelastic spectroscopy studies on cuprate superconductors by the author in collaboration with the Physics Departments of the Univ. of Rome “La Sapienza” and of Pavia, and with the Dept. of Chemistry of the Univ. of Genova (Italy). The complex moduli of YBCO, LSCO and Ru-1212 have been measured between 1 and 900 K at acoustic frequencies over the complete doping ranges, providing information on the dynamics and ordering of non-stoichiometric O, but also unique information on lattice and charge excitations, especially in LSCO. In fact, while the magnetic, dielectric, NMR and muon spectroscopies are dominated by the single charge or spin fluctuations, the anelastic spectroscopy is insensitive to them and may probe the collective charge and spin motions through their weak coupling to strain. In this manner it has been possible to probe the slow fluctuations of the hole stripes in the depinning regime and when they act as walls between antiferromagnetic domains in the cluster spin glass phase. In LSCO it was also possible to probe collective solitonic and tunneling-driven local dynamics of the layers of O octahedra.