Talk down to someone

Question

What is this phrase actually used for? "Talking to someone in a condescending manner " or "talking to someone in simple terms" or does it mean both?

Source 1:(Cambridge Dictionary) https://dictionary.cambridge.org/dictionary/english/talk-down-to-someone

to speak to someone in a simple way, as if the person cannot understand things as well as you can:

Our history teacher never talks down to us.

Or

Source 2: (The Collins Dictionary) https://www.collinsdictionary.com/dictionary/english-thesaurus/talk-down-to-someone

in the sense of condescend to:

She never talked down to her students.

Does it mean both of the things? If not then what can be used to mean "talking to someone in simple terms i.e. easy, layman's language" as in The Cambridge Dictionary?

Answer 1

To talk down to someone means to speak to them as if you think they are stupid, naive or ignorant; it is always considered insulting. This meaning is not as clear in the Cambridge definition as the Collins one, although the explanation "as if the person cannot understand things as well as you can" does convey that. To imply to someone that you are more clever than they are, or know more than they do, is deeply insulting.