$$\{ x_{i} \}_{i \in I} \; \text{NET} \; \underbrace{I}_{\text{VFOs}} \to X$$
$$x \in \overline{X} \iff \exists \; \text{NET} \; \underbrace{x_{i}}_{\in X} \to x$$
$I$ = neighbourhoods of $x$ with $A \geq B \iff A \subset B$.

$\{ \emptyset, X \}$ - all nets in $X$ will converge to all points in $X$.