  The aim of the paper is to give an `elementary' introduction to the theory of
modules over operads and discuss three prominent examples of these objects -
simplex, associahedron (= the Stasheff polyhedron) and cyclohedron (= the
compactification of the space of configurations of points on the circle).
  Keywords: (right) module over an operad, module associated to a cyclic
operad, Koszul module over an operad.
