The class of Short Gamma Ray Bursts still looks mysterious, despite
the recent discoveries of their X-ray and optical afterglows. Short
and Long Gamma Ray bursts are thought to have different progenitors:
merger of two collapsed object and single massive star collapse,
respectively. However, in both classes it is believed that the burst
is powered by accretion onto the newly born black hole.  Predictions
of this scenario can be directly tested. The modeling of short GRB
spectra shows that they are, on average, harder than long
events. However, time resolved spectral analysis shows that short GRB
spectra are consistent with the first seconds of the emission of long
GRBs.  The redshift distribution of short bursts still represents a
puzzle with respect to the expectation of finding them, most likely,
in late type galaxies. Finally, the energetics of short and long
events looks different whereas there is a good agreement between the
two population luminosities.