Suppose we have a binary variable $x$ and a non-negative continuous variable $y$. How can we linearize the product $x y$?
Suppose we can give a finite upper bound for $y$ called $M$. Then this constraint can easily be linearized by using the so-called big $M$ method. We introduce a new variable $z$ that should take the same value as the product $x y$.
Notice that the product which we model by $z$ equals zero if $x = 0$ but $z$ can take any value between $0$ and $M$ if $x = 1$. We can model this by using $z \leq x M$. Next, the product is always non-negative and smaller than $y$, thus $z\geq 0$ and $z \leq y$.
It is left to force $z$ to equal $y$ in case $x = 1$ which we obtain with $$ z \geq y - (1 - x)M. $$