He talks quickly . A Preposition is a word which comes before a noun or pronoun to form a phrase modifying another word in the sentence. The prepositional phrase nearly always functions as an adjective or adverb. Ivan went to the store with Emiko. Notice that this prepositional phrase is acting like an adverb.
Conjunctions join words, phrases or clauses.
They indicate the relationship between the elements they join. These are Adverbs that connect, so they act as conjunctions.