A prepositional phrase is a particle with the form of "preposition - [article] - nominal phrase." You shouldn't end sentences with prepositions. However, you may end sentences with the word preposition, or with a prepositional phrase, like I did in the previous sentence. Did you know that the word "preposition" literally means "in front of," which is also where the preposition sits in the phrase?
Dear lord, this is the sort of grammar up with which I will not put! In the next post, you must use no prepositions.