  One of the most intriguing features of quantum physics is the non-locality of
correlations that can be obtained by measuring entangled particles. Recently,
it has been noticed that non-locality can be studied without reference to the
Hilbert space formalism. I review here the properties of the basic mathematical
tool used for such studies, the so called Popescu-Rohrlich-box, in short
PR-box. Among its feats, are the simulation of the correlations of the singlet
and of other non-local probability distributions. Among its features, the
"anomaly of non-locality" and a great power for information-theoretical tasks.
Among its failures, the impossibility of reproducing all multi-partite
distributions and the triviality of the allowed dynamics.

Quantum Physics