  Neutron stars are unique testbeds for exploring the physics of strongly
interacting matter in extreme regimes of density, temperature, and isospin that
are not accessible anywhere else in the universe. The nature of neutron star
matter can now be probed with gravitational-waves (GWs) from binary driven by
nonlinear gravity, where phenomena such as tidal effects lead to characteristic
matter-dependent GW signatures. We focus here on the dominant tidal GW imprints
that were most relevant for the event GW170817. We review the role of the tidal
deformability parameter, its definition, computation, and relation to the
equation of state. We briefly discuss the implications of GW170817,
representing the first-ever constraints on tidal deformability from GW data.
Finally, we outline opportunities and challenges for probing subatomic physics
with GWs, as the measurements will become more precise and will probe a
diversity of the binary neutron star population in the coming years.
