The Wiki article on the Feynman-Kac formula says:
Applying Itô's Lemma to the process $$Y(s) = e^{-\int_t^s V(X_\tau,\tau)\, d\tau} u(X_s,s)+ \int_t^s e^{-\int_t^r V(X_\tau,\tau)\, d\tau}f(X_r,r)dr$$ one gets \begin{align}dY = {} & d\left(e^{- \int_t^s V(X_\tau,\tau)\, d\tau}\right) u(X_s,s) + e^{- \int_t^s V(X_\tau,\tau)\, d\tau}\,du(X_s,s) \\[6pt] & {} + d\left(e^{- \int_t^s V(X_\tau,\tau)\, d\tau}\right)du(X_s,s) + d\left(\int_t^s e^{- \int_t^r V(X_\tau,\tau)\, d\tau} f(X_r,r) \, dr\right)\end{align}
I know what Itô's Lemma says, but I can't see how it relates here. What's our '$f$'? What was the drift and diffusion terms? I can't see anything that resembles them in the definition of $Y$.