Extracting predictions from Supergravity/Superstring for the effective theory below the Planck scale

The connection between Superstring theory and the low–energy world is analyzed. In particular, the soft Supersymmetry–breaking terms arising in Supergravity theories coming from Superstrings are computed. Several solutions proposed to solve the $\mu$ problem, and the $B$ soft term associated, are discussed. The issue of gauge coupling constants unification in the context of Superstrings is also discussed.