  The fireshell model for Gamma-Ray Bursts (GRBs) naturally leads to a
canonical GRB composed of a proper-GRB (P-GRB) and an afterglow. P-GRBs,
introduced by us in 2001, are sometimes considered "precursors" of the main GRB
event in the current literature. We show in this paper how the fireshell model
leads to the understanding of the structure of GRBs, with precise estimates of
the time sequence and intensities of the P-GRB and the of the afterglow. It
leads as well to a natural classification of the canonical GRBs which overcomes
the traditional one in short and long GRBs.
