  We rehearse the physical and theoretical considerations that define the
nature of Brown Dwarfs, in particular the maximum mass for a Brown Dwarf (set
by the Hydrogen-Burning Limit) and the minimum mass for a Brown Dwarf (set by
the Opacity Limit). We then review the range of mechanisms that have been
invoked to explain the formation of Brown Dwarfs and their statistical
properties. These include turbulent fragmentation, fragmentation of filaments
and discs, dynamical ejection of stellar embryos, and photoerosion. The primary
contenders would seem to be turbulent fragmentation and disc fragmentation, and
the observations needed to evaluate their relative importance may soon be
available.
