Recently there has emerged
a new theory of curves over a finite field. This theory is exciting in that it establishes
previously unknown analogies between cyclotomic fields and function fields over a
finite field. An extremely important aspect of this work is a new type of L-series for
these function fields. These L-series bear quite remarkable and exciting similarities to
classical L-series of number fields. The purpose of this paper is to describe these new
L-series in detail.