How to use *todo*

I am self-studying Spanish, so let me ask you Spanish speakers questions here. One of my new vocab today is *todo*. On the dictionary, I see some example sentences, and I assume that if the nouns after the word *todo* is countable, it is *todos*, and if it is uncountable, it is *todo*. Is what I am understanding correct?

E.g.

todos las mujeres

toda la noche