  In these lectures we give an overview of the duality between gravitational
theories of massless higher spin fields in AdS and large N vector models. We
first review the original higher spin/vector model duality conjectured by
Klebanov and Polyakov, and then discuss its generalizations involving vector
models coupled to Chern-Simons gauge fields. We proceed to review some aspects
of the theory of massless higher spins, starting with the Fronsdal equations
for free fields and moving on to the fully non-linear Vasiliev equations in
four dimensions. We end by reviewing some recent tests of the higher
spin/vector model duality at the level of correlation functions and one-loop
partition functions.
