I will discuss the major uncertainties regarding the geometry,
energetics, and environment of the first EM/GW binary neutron star
merger GW170817.  In particular I will look at the origin of the radio
emission, how it differs from the early-time optical/infrared
emission, and what that tells us about how the explosion proceeded.  I
will show how constraints from the radio lightcurve, polarization, and
Very Long Baseline Interferometry helped provide evidence for a broad,
mildly relativistic “cocoon” along with a narrow jet.  This
broke degeneracies in the gravitational wave data analysis to provide
inclination constraints and improved measurements of the Hubble
Constant.