  In string theory, D-branes can be expressed as a configuration of infinitely
many lower dimensional D-branes. Using this relation, the worldvolume theory of
D-branes can be regarded as the worldvolume theory of the infinitely many lower
dimensional branes. In the description in terms of the lower dimensional
branes, some of the worldvolume coordinates become noncommutative. Actually
this noncommutative theory can be regarded as noncommutative Yang-Mills theory.
Therefore the worldvolume theory of D-branes have two equivalent descriptions,
namely the usual static gauge description using ordinary Yang-Mills theory and
the noncommutative description using noncommutative Yang-Mills theory. It will
be shown that these two descriptions correspond to two different ways of gauge
fixing of the reparametrization invariance and its generalization. We will give
an explicit relation between commutative gauge field and noncommutative gauge
field in semiclassical approximation, when the gauge group is U(1).
