Noun Clause which Began With Question Words

A clause is a group of related words. It contains a subject and a verb.
A noun clause is a dependent which cannot stand alone as a sentence. It must be connected to an independent clause  (a main clause). The following  question words can be used to introduce a noun clause : what, where, when, why, how, who, whom, which, whose.
A noun clause can be used as a subject or an object.

Examples :

Subject	Verb	Object
I	enjoy	It
I	Enjoy	What I do
It	confuses	Me
What he says	confuses	Me

Noun Clause

Noun clause is an entire clause which takes the place of a noun in another clause or phrase. Like a noun, a noun clause acts as the subject or object of preposition , answering the questions “who(m)” or “what”.
A noun clause takes the place of a noun.
Noun clause can function as :
A subject of a verb : That they should say surprise me.

An object of transitive verb : She denied that she had written a letter.

An object of preposition : Pay careful attention to what I am going to say.

In apposition to a noun or pronoun : Your statement that you found the money in the street will not be believed.

A complement of a verb of incomplete prediction ; His great faer is that he may fail.

English Grammar : Clause

Learn Grammar | English Grammar : Clause | Clause is a group of words that already have a subject and predicate are used to express an idea or complete thoughts. Due to already have a subject and predicate of the clause could be called a sentence.
When a sentence has more than one clause, ie one as independent clause and the other as a dependent clause, the sentence would be complex.

Thus the clause which forms a complex sentence is as follows:
a. Consisting of one as a main clause (independent clause, main clause, independent clause)
b. Consists of one or more subordinate clauses (clause section, clause bound, dependent clause.)