What does $|V|=O(|E|)$ mean?

Question

I was reading about Dijkstra's algorithm from this Stanford University lecture presentation. On page 18 it says Dijkstra's algorithm is $O(|V|\log|V|+|E|\log|V|)$ and I understand why. But then it says that $O(|V|\log|V|+|E|\log|V|) = O(|E|\log|V|)$, because $|V|=O(|E|)$. What does $|V|=O(|E|)$ mean and why is it so?