"Noun phrase" is a term from linguistics, in particular,
transformational grammar. "Noun clause" is not normally used in
linguistics. It is a term from traditional grammar.
A noun phrase is a group of words in which a noun or pronoun is the head. A single noun by itself can be a noun phrase.
In
We answered all your questions.
"we" is a noun phrase, and "all your questions" is a noun phrase.
A noun clause is a clause which functions as a noun. The most
typical example is a "that"-clause after a verb of reporting.
In
Paul told us that he was tired.
"that he was tired" is a noun clause. It functions as a noun, as is seen by comparing with
Paul told us the truth.
CJ