  The state of art in studying thermodynamic properties of hot and dense
nuclear matter is reviewed with the special emphasis on the
confinement-deconfinement transition between hadron matter and quark-gluon
plasma. The most popular models used for describing deconfinement are analysed,
including statistical bootstrap models, pure phase models, the model of
clustered quarks, and the string-flip potential model. Predictions of these
models are compared with the lattice numerical simulations. It is concluded
that precursor fluctuation effects must be taken into account in order to get a
realistic description of deconfinement transition. Deconfinement cannot be
considered as a transition between pure hadron and quark-gluon phases.
Quark-gluon plasma and hadron clusters are different quantum states of the same
system, so that any statistical model pretending to treat nuclear matter under
extreme conditions must incorporate the probability of these different
channels.
