An independent clause and a dependent clause.
An independent clause is a clause that can stand alone as a sentence (i.e., it expresses a complete thought). However, a dependent clause (or subordinate clause) is one that cannot stand alone as a complete sentence because it does not express a complete thought. Cause it is not a complete thought, it is dependent on being attached to an independent clause to form a sentence. The link between a dependent clause and an independent clause will often be a subordinating conjunction or a relative pronoun.
