Among the three types of conjunctions, this is probably the most common one. The main function of coordinating conjunctions is to join words, phrases, and clauses together, which are usually grammatically equal. Aside from that, this type of conjunctions is placed in between the words or groups of words that it links together, and not at the beginning or at the end.
This type of conjunctions is used in linking two clauses together. Aside from the fact that they introduce a dependent clause, subordinating conjunctions also describe the relationship between the dependent clause and the independent clause in the sentence.
The correlative conjunctions are simply pairs of conjunctions which are used to join equal sentence elements together."