A noun is a single word that can have one of three basic jobs: subject of a verb, like "Cats are cute"; object of a verb, like "I like coffee"; and object of a preposition, like "Put it in water". A noun phrase is more than one word doing a noun's job, for example, in "Siamese cats are cute", "Siamese cats" is a noun phrase; in "I like strong, black coffee", "strong, black coffee" is a noun phrase and in "Put it in the water", "the water" is a noun phrase. A noun clause is more than one word plus a verb doing a noun's job (like a mini-sentence), for example, in "What he says isn't important", "What he says" is a noun clause acting as the subject of "is"; in "I didn't know (that) you were here", "(that) you were here" is a noun clause acting as the object of "know" and in "I don't want to listen to why you were late", "why you were late" is a noun clause acting as the object of "to". As you can see, they take the form QUESTION WORD/(THAT) + SUBJECT + VERB (+ OBJECT). I hope this helps!

clause: group of words within a sentence, usually with a verb eg: That is the girl who is my friend. in this case "who is my friend" would be a clause, specifically, a relative clause, ("who" is a relative pronoun referring back to the noun: "girl") "my friend" is a noun phrase; it is a phrase because it is within a clause, and the head of the phrase (the most important component) is a noun. "My" is a premodifier of the noun.