"Contents of the lectures. - For the convenience of the reader, and to set the scene, I will recall a few basic facts (definitions, constructions and examples) from the theory of integrable systems. I will also explain some classical examples, in connection with the Arnold-Liouville theorem. I will then describe the moduli space and its Poisson structure from two points of view (infinite dimensional, a la Atiyah-Bott, finite dimensional, d la Fock-Roslyi). The last part is devoted to the description of Goldman's functions and to the examples."