If $X$ is a scheme, what do we usually mean by $|X|$?

Question

Let $X$ be a scheme. What do we usually mean by $|X|$?

The context: we have functor $F$ from the category of schemes to some another category, which I call $A$, where the elements are schemes with some special property, and morphisms are the usual morphisms of schemes.

Let $f$ be a morphism of schemes. The claim is that $F(f)$ retains many of the topological properties of $f$, since $|X|=|F(X)|$.

Answer 1

$|X|$ usually means the topological space of closed points of $X$ endowed with the Zariski topology.