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

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?