Giovanni Gallavotti Fluctuation relation, fluctuation theorem, thermostats and entropy creation in non equilibrium statistical Physics (62K, latex) ABSTRACT. A unified viewpoint is presented in margin to the ``Work, dissipation and fluctuations in nonequilibrium physics'' Bruxelles 22-25 March, 2006, where the topics were discussed by various authors and it became clear the need that the very different viewpoints be consistently presented by their proponents.