Gamma Ray Bursts: basic facts and ideas
  The recent years witnessed a dramatic improvement in our knowledge of the
phenomenology and physics of Gamma Ray Bursts (GRBs). However, our "pillars of
knowledge" remain a few, while many aspects remain obscure and not understood.
There is no general agreement on the radiation mechanism of the prompt
emission, nor on the process able to convert the bulk motion of the fireball
into random energy of the emitting leptons. The afterglow phase can now be
studied at very early phases, showing an unforeseen phenomenology, still to be
understood. In this context, the detection of ~GeV emission from ~10 per cent
of GRBs, made possible by the {\it Fermi} satellite, can hopefully shed light
on some controversial issues.
