This paper contains a short and simplified proof of
desingularization over fields of characteristic zero, together
with various applications to other problems in algebraic geometry
(among others, the study of the behavior of desingularization of
families of embedded schemes, and a formulation of desingularization
which is stronger than Hironaka's). Our proof avoids the use of
the Hilbert-Samuel function and Hironaka's notion of normal flatness:
First we define a procedure for principalization of ideals
(i.e. a procedure to make an ideal invertible), and then
we show that desingularization of a closed subscheme $X$ is
achieved by using the procedure of principalization for the ideal
${\mathcal I}(X)$ associated to the embedded scheme $X$. The
paper intends to be an introduction to the subject, focused on the
motivation of ideas used in this new approach, and particularly on
applications, some of which do not follow from Hironaka's proof.