  The aim of these lectures is to give an introduction to several topics which
lie at the intersection of string theory, gravity theory and gravity
phenomenology. One successively reviews: (i) the "membrane" approach to the
dissipative dynamics of classical black holes, (ii) the current experimental
tests of gravity, and their theoretical interpretation, (iii) some aspects of
the string-inspired phenomenology of the gravitational sector, and (iv) some
possibilities for observing string-related signals in cosmology (including a
discussion of gravitational wave signals from cosmic superstrings).
