  We give an introduction to the compactification of the moduli space of
surfaces of general type introduced by Koll\'ar and Shepherd-Barron and
generalized to the case of surfaces with a divisor by Alexeev. The construction
is an application of Mori's minimal model program for 3-folds. We review the
example of the projective plane with a curve of degree d > 3. We explain a
connection between the geometry of the boundary of the compactification of the
moduli space and the classification of vector bundles on the surface in the
case H^{2,0}=H^1=0.
