  We review the current state of research on electromagnetic probes in the
context of heavy-ion collisions. The focus is on thermal photons and dileptons
which provide unique insights into the properties of the created hot and dense
matter. This review is intended to provide an introductory overview of the
topic as well as a discussion of recent theoretical and experimental results.
In particular, we discuss the role of vector-meson spectral functions in the
calculation of photon and dilepton rates and present recent results obtained
from different frameworks. Furthermore, we will highlight the special role of
photons and dileptons to provide information on observables such as the
temperature, the lifetime, the polarization and the electrical conductivity of
the produced medium as well as their use to learn about chiral symmetry
restoration and phase transitions.
