Advantage Function

Definition

$A_{\pi }(s,a)=q_{\pi }(s,a)-v_{\pi }(s)$ An advantage function $A_{\pi }(s,a)$ is the difference between the Action-Value Function $q_{\pi }(s,a)$ and the State-Value Function $v_{\pi }(s)$ under policy $\pi$. It represents how much better it is to take action $a$ in state $s$ compared to the average action.