Like wh-questions, relative clauses come in two major types: (1) those that have the relative pronoun as the subject of the clause and (2) those that have the relative pronoun as something other than the subject of the clause (object or complement or object of a preposition).
In addition, relative clauses can be added to nouns in just about any part of a sentence--at the beginning, in the middle, and at the end of sentences. Let's analyze the location and type of relative clause in each of the following sentences: