  The origin of GRBs have been a mystery for almost 30 years. The afterglow
observed in the last few years enabled redshift determination for a handful of
bursts, and the cosmological origin is now firmly established. Though the
distance scale is settled, there still remains orders of magnitude uncertainty
in their rate and in the total energy that is released in the explosion due to
the possibility that the emission is not spherical but jet-like. Contrary to
the GRB itself, the afterglow can be measured up to months and even years after
the burst, and it can provide crucial information on the geometry of the
ejecta. We review the theory of afterglow from jets and discuss the evidence
that at least some of the bursts are not spherical. We discuss the prospects of
polarization measurements, and show that this is a powerful tool in
constraining the geometry of the explosion.
