what does it mean by those equations of random process?

Question

What does it mean by this notation $(1_Y)$ of random process,

$$ \Psi=\frac{1}{n}\sum_{i=1}^{n}1_{Y(X)\rangle s} $$ and $$ \Psi=\int 1_{Y(X)\rangle s} f(x) dx $$

where $s$ is a given threshold and $f(x)$ is the joint pdf of $X$.