The document explains noun clauses, defining them as dependent clauses that serve the same function as nouns, acting as subjects, objects, or complements in sentences. It provides examples of noun clauses, the roles they play, and highlights the distinction between 'if' and 'whether' in formal writing, emphasizing that 'whether' should be used for two possibilities while 'if' is for conditional sentences. Various question words relevant to noun clauses are also noted, along with examples for better understanding.