The document discusses noun clauses and how they differ from nouns and noun phrases. A noun clause is a group of words that functions as a noun, containing a subject and verb, such as "where she was yesterday." Noun clauses can serve as the subject or object of a sentence. They differ from noun phrases which do not contain both a subject and verb. The document provides examples to distinguish noun clauses from nouns and noun phrases. It also discusses dependent and independent clauses, with dependent clauses being incomplete sentences that must be connected to independent clauses.