  We discuss the factors influencing the formation and gravitational
fragmentation of protostellar discs. We start with a review of how observations
of prestellar cores can be analysed statistically to yield plausible initial
conditions for simulations of their subsequent collapse. Simulations based on
these initial conditions show that, despite the low levels of turbulence in
prestellar cores, they deliver primary protostars and associated discs which
are routinely subject to stochastic impulsive perturbations; consequently
misalignment of the spins and orbits of protostars are common. Also, the
simulations produce protostars that collectively have a mass function and
binary statistics matching those observed in nearby star formation regions, but
only if a significant fraction of the turbulent energy in the core is
solenoidal, and accretion onto the primary protostar is episodic with a duty
cycle > 3000 yr. Under this circumstance a core typically spawns between 4 and
5 protostars, with high efficiency, and the lower-mass protostars are mainly
formed by disc fragmentation. The requirement that a proto-fragment in a disc
lose thermal energy on a dynamical timescale dictates that {\bf there is a
sweet spot for} disc fragmentation at radii 70 AU < R < 100 AU and temperatures
10 K < T < 20 K, and this might explain the Brown Dwarf Desert.
