  These notes are an introduction to basic properties of Andre-Quillen homology
for commutative algebras. They are an expanded version of my lectures at the
summer school: Interactions between homotopy theory and algebra, University of
Chicago, 26th July - 6th August, 2004. The aim is to give fairly complete
proofs of characterizations of smooth homomorphisms and of locally complete
intersection homomorphisms in terms of vanishing of Andre-Quillen homology. The
choice of the material, and the point of view, are guided by these goals.
