  This TASI lecture covers the material in hep-th/9205026. It reviewed the
theory of effective strings, with particular emphasis on the manner in which
Lorentz invariance is represented. The quantum properties of an example of an
effective string are derived from the underlying field theory. A comparison is
made with what one would expect if one assumed that quantum effective strings
were governed by fundamental string actions such as the Nambu-Goto or the
Polyakov actions. It is shown that the requirements on dimensions for
consistent quantizations of fundamental strings imply no contradictions for
effective strings.
