You must be confused because the last word is missing the "e" at the end. It was one too many letters for the title, so it didn't take.
I'm sure that clears it up for you.
For the rest of you, it simply means that in order to have well defined rules for the perturbative calculation of quantities of interest in an interacting quantum field theory in curved spacetime, it is necessary to construct Wick polynomials and their time ordered products for the noninteracting theory.