General questions concerning the dynamics of systems with many degrees
of freedom are discussed, focussing on approach to equilibrium in sim
ple statistical mechnical models. The contrasts between the behavior o
f systems with short-range interactions and mean-field pictures in ter
ms of energy ''landscapes'' are emphasized. It is shown how much of th
e behavior of systems with short-range interactions can be described i
n terms of domain walls and their dynamics. Simple Ising magnetic mode
ls, both ferromagnets and spin glasses, are used as a paradigm.