A conjunction joins words, phrases, and sentences. There are three types of conjunctions: coordinating conjunctions, subordinating conjunctions, and correlative conjunctions. Coordinating conjunctions connect elements of equal importance and include FANBOYS conjunctions like "and" and "but." Subordinating conjunctions introduce dependent clauses and include conjunctions like "because" and "when." Correlative conjunctions work in pairs to connect elements, such as "both...and" and "either...or."