I first recall the various problems of real enumerative geometry out of which I could extract some integer valued invariants, providing some real counterpart to Gromov-Witten invariants. I then discuss sharpness of the lower bounds given by these invariants and some of their arithmetical properties. Finally, I present further results which guaranty the presence or absence of pseudo-holomorphic discs with boundary on a Lagrangian submanifold of a given symplectic manifold.