Calcul Moulien

This paper is an introduction to mould calculus as introduced by Jean Ecalle. We give a precise definition of moulds and describe there main properties. We translate mould symmetries (alterna(e)l and symetra(e)l) using non commutative formal power series in two given bialgebras. We apply this formalism to the problem of normal forms for vector fields and diffeomrophisms.