Explore the physics of tides in binary star systems in this comprehensive lecture from the Summer School on Gravitational-Wave Astronomy. Delve into the intricacies of gravitational wave signals, Newtonian theory, and mass multipole moments. Learn about Taylor expansions, symmetric trace-free tensors, and the relation between spherical harmonics and Cartesian coordinates. Gain insights into the potential in a star's exterior and its implications for binary systems. This lecture, delivered by Tanja Hinderer from the Max Planck Institute for Gravitational Physics, is part of a broader program covering various aspects of compact objects and gravitational wave astronomy.