  The Polyakov loop is the appropriate deconfinement order parameter for
Yang-Mills theories without quarks or with quarks in the adjoint representation
of the gauge group. However it is not a physical state of the theory so the
information regarding the center group symmetry must be transferred to the
physical states. We briefly review how this transfer of information takes
place. When adding quarks the center group is no longer a symmetry for matter
in the fundamental representation. This feature allows us to explain why color
deconfines when chiral symmetry is restored in hot gauge theories with massless
quarks. For quarks in the adjoint representation we show that while
deconfinement and the chiral transition do not coincide, entanglement between
them is still present. Finally, we discuss also the chemical potential driven
phase transition.
