  PBH formation requires high-density regions in the (random) density field
filling the primordial universe. While only the largest (and so rarest)
overdensities collapse to form PBHs, the rest cause large anisotropic stresses,
which are the source of GWs. We provide an overview of the theoretical aspects
of the GW backgrounds associated with PBHs from large primordial fluctuations.
We consider GW backgrounds associated with PBH formation, PBH reheating and
unresolved PBH binaries. We present several graphical summaries and
illustrations for the busy reader.
