  At the Relativistic Heavy Ion Collider (RHIC) collisions of heavy ions at
nucleon-nucleon energies of 200 GeV appear to have created a new form of matter
thought to be a deconfined state of the partons that ordinarily are bound in
nucleons.We discuss the evidence that a thermalized partonic medium, usually
called a Quark Gluon Plasma (QGP), has been produced. Then we discuss the
effect of this high-density medium on the production of jets and their pair
correlations. Next we look at direct photons as a clean electro-magnetic probe
to constrain the initial hard scatterings. Finally we review the developing
picture for the effect of this medium on the production of open heavy quarks
and on the screening by the QGP of heavy-quark bound states.
