What are they?
The first type of clause are the main clauses. All clauses follow a pattern, the pattern for main clauses is subject+verb=complete thought. Main clauses are an important part of sentences because if you don't have a main clause in your sentence then it isn't a sentence, it is a fragment. An example of a main clause would be "This pizza tastes surprisingly good." In this sentence "pizza" is the noun and "tastes" is the verb.
Subordinate clauses are the second type of clause. The pattern for subordinate clauses is subordinate conjunction+subject+verb=incomplete thought. Some examples of subordinate conjunctions are whenever, as and because. Remember that subordinate clauses by themselves do not make a complete sentence. An example of this would be "As Alice played with the toys"
Next is relative clauses. The pattern for relative clauses is relative pronoun or adverb+subject+verb=incomplete thought. Some relative pronouns and adverbs are whom, who, whose, and when, where, why. Relative clauses also are not sentences by themselves. An example of a relative clause would be "Why he drank soda"
A noun clause is a a group of words that is being used in the sentence as one noun, such as "You really do not want to know what Aunt Nancy puts in her stew." Aunt Nancy puts in her stew is the noun clause.