  This review aims at a critical discussion of the interplay between effective
interactions derived from various many-body approaches and spectroscopic data
extracted from large scale shell-model studies. To achieve this, our many-body
scheme starts with the free nucleon-nucleon (NN) interaction, typically
modelled on various meson exchanges. The NN interaction is in turn renormalized
in order to derive an effective medium dependent interaction. The latter is in
turn used in shell-model calculations of selected nuclei. We also describe how
to sum up the parquet class of diagrams and present initial uses of the
effective interactions in coupled cluster many-body theory.
