Prepositional Phrase
A prepositional phrase begins with a preposition and ends with a noun or a pronoun. Example: A small crowd formed behind the injured costumer. The preposition is 'behind' and the noun that ends the prepositional phrase is 'customer'.
Appositives
An appositive is a grammatical construction in which two elements, normally noun phrases, are placed side by side, with one element serving to identify the other in a different way. The two elements are said to be in appositive.