  I present a theory-guided review of RHIC data, arguing that they provide
strong evidence for formation of a thermalized quark-gluon plasma at RHIC.
Strong radial flow reflects high thermal pressure in the reaction zone. Large
elliptic flow proves that the pressure builds up quickly and the system
thermalizes on a very short time scale of less than 1 fm/c. The observed hadron
yields are consistent with statistical hadron formation from a quark-gluon
plasma, followed by immediate chemical decoupling due to strong radial
expansion. The observed suppression of jets appears to confirm the predicted
large energy loss suffered by hard partons moving through a quark-gluon plasma;
more work is required to quantitatively understand this effect. Source size
measurements using two-particle correlations do not seem to fit into this
picture; the origin of this discrepancy (``HBT puzzle'') is presently not
understood.

Nuclear Theory