Let $f:X \to Y$ be a morphism of schemes. Let $Br(X)$ be Brauer group of $X$. I heard $Br(-)$ is functrial, that is, there is induced map $f^*: Br(Y)\to Br(X)$.
How $f$ induces $f^*$, in other words, what is the map $f^*$ exactly ?
Thank your for your help.