The dilepton probe in heavy-ion collisions

Dileptons provide direct observables of the electromagnetic current-current correlator in the hot and/or dense medium formed in heavy-ion collisions. In this article an overview is given about the status of the theoretical understanding of the dilepton phenomenology in heavy-ion collisions from studies of the in-medium properties of hadrons and partons within many-body theory and about connections to fundamental questions concerning the chiral phase transition.