An introduction to topological defects in cosmology is given. We discuss
their possible relevance for structure formation. Especial emphasis is given on
the signature of topological defects in the spectrum of anisotropies in the
cosmic microwave background. We present simple analytic estimates for the CMB
spectrum on large and intermediate scales and compare them with the
corresponding approximations for models where initial perturbations are
generated during an inflationary epoch.Comment: LaTex file 18pages, 5 postscript figures Contribution to the
Proceedings of the conference on 'Topolocigal Defects in Cosmology' in Roma,
La Sapienz
