  An elementary introduction to the physics of quark-gluon plasma is given. We
start with a sketchy presentation of the Quantum Chromodynamics which is the
fundamental theory of strong interactions. The structure of hadrons built up of
quarks and gluons is briefly discussed with a special emphasis on the
confinement hypothesis. Then, we explain what is the quark-gluon plasma and
consider why and when the hadrons can dissolve liberating the quarks and
gluons. The heavy-ion collisions at high-energies, which provide a unique
opportunity to get a droplet of the quark-gluon plasma in the terrestrial
conditions, are described. We also consider the most promising experimental
signatures of the quark-gluon plasma produced in nucleus-nucleus collisions. At
the end, the perspectives of the quark-gluon plasma studies at the future
accelerators are mentioned.
