  We show that the deconfinement phase transition in the pure Yang-Mills theory
can be characterized by the change of behaviour the spatial 't Hooft loop,
V(C). In the confining phase V has a perimeter law behaviour V(C)= exp{-mP(C)},
while in the deconfined phase it has the area law behaviour V(C)= exp{-\alpha
S(C)}. We show that the area law behaviour of the 't Hooft loop is intimately
related to the plasma-like distribution of the color charges in the hot QCD
vacuum. We also show that the "dual string tension" \alpha is equal to the
"wall tension" of the Z_N domain walls previously calculated by Bhattacharya
et.al. All these properties generalize immediately to other nonabelian theories
without fundamental charges, such as supersymmetric Yang Mills. In theories
with fundamental charges the 't Hooft loop presumably has the area law
behaviour already at zero temperature and therefore is not a good order
parameter in the strict sense.
