  We investigate the properties of voids and void galaxies in the
\texttt{TNG300} simulation. Using a luminous galaxy catalog and a spherical
void finding algorithm, we identify 5,078 voids at redshift $z = 0$. Within the
voids, mass does not directly trace light. Instead, the mean radial
underdensity profile as defined by the locations of void galaxies is
systematically lower than the mean radial underdensity profile as defined by
the dark matter (i.e., the voids are more ``devoid'' of galaxies than they are
of mass). Within the voids, the integrated underdensity profiles of the dark
matter and the galaxies are independent of the local background density (i.e.,
voids-in-voids vs.\ voids-in-clouds). Beyond the void radii, however, the
integrated underdensity profiles of both the dark matter and the galaxies
exhibit strong dependencies on the local background density. Compared to
non-void galaxies, void galaxies are on average younger, less massive, bluer in
color, less metal enriched, and have smaller radii. In addition, the specific
star formation rates of void galaxies are $\sim 20$\% higher than non-void
galaxies and, in the case of galaxies with central supermassive black holes
with $M_{\rm BH} \gtrsim 3\times 10^6 h^{-1} M_\odot$, the fraction of active
void galaxies is $\sim 25$\% higher than active non-void galaxies.
