  We provide a pedagogical approach to gravitational waves in cosmology with
focus on gravitational wave signals related to primordial black holes. These
lectures notes contain more details than one is able to present in the two
two-hour lectures they are meant to and, as such, they should be thought as a
complementary material. The main aim of these lectures is that, by the end, one
obtains a certain degree of intuition on gravitational waves in cosmology and
understands the basic features of scalar induced gravitational waves. We also
highlight must-check properties of induced gravitational waves as well as
current issues regarding secondary gravitational waves in cosmology. Throughout
the lecture we provide exercises, supplementary information and activities with
public codes to be ready to derive your own results.
