# Semantic difference between \amalg and \coprod for disjoint union

What's the semantic difference between \amalg and \coprod for disjoint unions?

I used to use \amalg for binary operations like X \amalg Y and \coprod for operators like \coprod_\lambda X_\lambda. But I realized that I don't know any literature or manual how these similar-looking symbols should be used. Please tell me if you have any.