  The lectures examine several problems related to non-equilibrium fluctuations
of interfaces and flux lines. The first two introduce the phenomenology of
depinning, with particular emphasis on interfaces and contact lines. The role
of the anisotropy of the medium in producing different universality classes is
elucidated. The last two lectures focus on the dynamics of lines, where
transverse fluctuations are also important. We shall demonstrate how various
non-linearities appear in the dynamics of driven flux lines. The universality
classes of depinning, and also dynamic roughening, are illustrated in the
contexts of moving flux lines, advancing crack fronts, and drifting polymers.
