  Correlations are a very important tool in the study of multipartite systems,
both for classical and quantum ones. The discussion about the quantum nature of
correlations permeates Physics since Einstein, Podolski and Rosen published
their famous article criticizing quantum mechanics. Here we provide a short
review about the quantum nature of correlations, discussing both its
theoretical and experimental aspects. We focus on quantum discord and related
measures. After discussing their fundamental aspects (theoretically and
experimentally), we proceed by analysing the dynamical behaviour of
correlations under decoherence as well as some applications in different
scenarios, such as quantum computation and relativity, passing through critical
and biological systems.
