In Shreve's Finance and Stochastic calculus, definitions are:
Forward Price: The $T$-forward price $For_S(t,T)$ of this asset at time $t$, where $0\leq t\leq T$, is the value of $K$ that makes the forward contract have no-arbitrage price zero at time $t$. ($K$ is the striking price)
Futures price: The futures price of an asset whose value at time $T$ is $S(T)$ is \begin{align*} Fut_S(t,T)=E(S(T)|\mathcal{F}(t)) \end{align*}
They seem to be different from the price of an asset derivative, which satisfy the formula: \begin{align*} V(t)= \frac{1}{D(t)}E(D(T)V(T)|\mathcal{F}(t)) \end{align*} where $V(T)$ is the pay-off. (Where $D(t)$ is the discount process)
So my question is: What do these two concepts really mean? Does anyone have any comments?
Thanks in advance!