  The mechanism responsible for the prompt emission of gamma-ray bursts (GRBs)
is still a debated issue. The prompt phase-related GRB correlations can allow
to discriminate among the most plausible theoretical models explaining this
emission. We present an overview of the observational two-parameter
correlations, their physical interpretations, their use as redshift estimators
and possibly as cosmological tools. The nowadays challenge is to make GRBs, the
farthest stellar-scaled objects observed (up to redshift $z=9.4$), standard
candles through well established and robust correlations. However, GRBs
spanning several orders of magnitude in their energetics are far from being
standard candles. We describe the advances in the prompt correlation research
in the past decades, with particular focus paid to the discoveries in the last
20 years.
