  Heavy quarkonium theory has seen significant progress over the past years.
Not only has the community steadily improved the understanding of fully
equilibrated quarkonium using first principles lattice QCD studies, but it has
taken major steps towards developing a genuine dynamical understanding of
quark-antiquark pairs immersed in a hot medium by embracing the paradigm of
open quantum systems. We review recent developments, placing an emphasis on
quarkonium real-time dynamics.
