We review some basic concepts of Relativistic Heavy Ion Physics and discuss
our understanding of some key results from the experimental program at the
Relativistic Heavy Ion Collider (RHIC). We focus in particular on the early
time dynamics of nuclear collisions, some result from lattice QCD, hard probes
and photons.Comment: 11 pages, 3 figures; delivered at ISNP 2009, published in Praman