Let $X$ be a smooth projective variety over a field $k$ of characteristic zero, and let $D$ be a simple normal crossing divisor inside $X$ having irreducible components $D_i$. Further let $x \in X$ be a closed point belonging to (at least) one of these components, say $D_0$.

How should I think of the elements in

$\Gamma(Spec(\mathcal{O}_{X, x})-D_0, \mathbb{G}_m)$?

What is the order at $x$ of such an element?

Thanks for your help!