In this lecture, we give a brief review of what theorists now know,
understand, or guess about static and kinetic properties of quark--gluon
plasma. A particular attention is payed to the problem of physical
observability, i.e. the physical meaningfulness of various characteristics of
QGP discussed in the literature.Comment: 35 pages LaTeX, 3 Postscript figures included by epsf.sty are now
fixed and printable, uses axodraw.sty included in the package. Some
references added and minor stylistic changes made. Lecture at the XXIV ITEP
Winter School (Snegiri, February 1996
