  These notes cover part of the lectures presented by Andrea Maselli for the
59th Winter School of Theoretical Physics and third COST Action CA18108
Training School 'Gravity -- Classical, Quantum and Phenomenology'. The school
took place at Palac Wojan\'ow, Poland, from February 12th to 21st, 2023. The
lectures focused on some key aspects of black hole physics, and in particular
on the dynamics of particles and on the scattering of waves in the
Schwarzschild spacetime. The goal of the course was to introduce the students
to the concept of black hole quasi normal modes, to discuss their properties,
their connection with the geodesic motion of massless particles, and to provide
numerical approaches to compute their actual values.
