A prepositional phrase is a group of words that begins with a proposition and ends with a noun or a pronoun. This noun or pronoun is called the "object of the preposition."

A preposition is a word that shows the relationship of a noun or pronoun to some other word in a sentence.

A preposition can have  a compound object, two or more nominatives that function as the direct object of the preposition. Note that objects must appear in the objective case.