  Long Gamma-Ray Bursts (GRBs) are the brightest electromagnetic explosions in
the Universe, associated to the death of massive stars. As such, GRBs are
potential tracers of the evolution of the cosmic massive star formation,
metallicity, and Initial Mass Function. GRBs also proved to be appealing
cosmological distance indicators. This opens a unique opportunity to constrain
the cosmic expansion history up to redshifts 5-6. A brief review on both
subjects is presented here.
