The phase structure of QCD

We review recent results on the phase structure of quantum chromodynamics (QCD) and bulk QCD thermodynamics. In particular, we discuss how universal critical scaling related to spontaneous breaking of the chiral symmetry manifests itself in recent lattice QCD simulations and how the knowledge on non-universal scaling parameters can be utilized in the exploration of the QCD phase diagram. We also show how various (generalized) susceptibilities can be employed to characterize properties of QCD matter at low and high temperatures, related to deconfining aspects of the QCD transition. Finally, we highlight the recent efforts towards understanding how lattice QCD calculation can provide input for our understanding of the matter created in heavy ion collisions and in particular on the freeze-out conditions met in the hydrodynamic evolution of this matter. (paper)