I will review the basics characteristics of the GRB phenomenology
and the current ideas to explain them.
Then I will discuss some recently found correlations between
the energy emitted during the prompt phase and the spectral
peak of the gamma-ray spectrum, Epeak.
By accounting of the aperture of the jet, one derives a very tight
correlation between the collimation corrected energy and Epeak,
so tight that it allows to consider GRBs as standard candles.
We find very encouraging results that emphasize the cosmological GRB
role.