The independent clause is the main part of the sentence, expresses a complete thought, and could stand by itself and still make sense. The subordinate clause gives additional information, but does not express a complete thought, and cannot stand by itself. The dog , who is usually very good, ate my homework. If you get hungry, there's ice cream in the freezer. In the first two examples, the subordinate clause is of a particular kind called a relative clause.
Relative clauses describe nouns or pronouns and generally begin with which, that, whom, whose, who.
Notice that in the first example no commas set off the relative clause, while there are commas in the second example. In the example above, the relative clause restricts the set of people who shouldn't throw stones to those who live in glass houses. The rest of us don't have to worry. The second example is called a nonrestrictive relative clause. It gives only parenthetical information about the noun, but does not serve to identify the noun or give other necessary information, as the restrictive type does.