  In addition to being a prime candidate for a fundamental unified theory of
all interactions in nature, string theory provides a natural setting to
understand gauge field theories. This is linked to the concept of "D-branes":
extended, solitonic excitations of string theory which can be studied using
techniques of string theory and which support gauge fields localized along
their world-volumes. It follows that the techniques of string theory can be
very useful even for those particle physicists who are not specifically
interested in unification and/or quantum gravity. In this talk I attempt to
review how strings help us to understand fields. The discussion is restricted
to 3+1 spacetime dimensions.
