Sentence #2 has the dependent clause. A dependent clause is a clause that can't stand alone in a sentence. "When she jumped into the pool" cannot stand alone. "When" is the subordinating conjunction that introduces the dependent clause.
This type of clause is called "dependent" because, in order to exist in a sentence, it needs a stronger, independent clause to connect to. "Subordinating conjunction" (when) refers to the word that makes this clause subordinate to the other, but enables it to connect.
All the other sentences have two independent clauses. Each of these two clauses can stand alone, independently, in the sentence. These two clauses could also stand alone to be independent sentences.
The words that connect these two independent clauses are called "coordinating conjunctions." They act to "coordinate" or "bring together" the two clauses. In these sentences, the coordinating conjunctions are "and," "or," and "but."