Answer: Prepositional phrase
Explanation: Prepositional phrases always start with a preposition and always end with a noun or a pronoun called the object of the preposition.
Let's look at an example.
A vase of flowers fell on the floor.
We have two prepositional phrases in this sentence. "Of flowers" would be one because "of" is a preposition and "flowers" is the object.
"On the floor" would be another prepositional phrase because "on" is a preposition and "floor" is the noun that it works with.