When the prepositional phrase functions as an adverb by modifying a verb, an adjective, or an adverb, it is called an adverbial phrase.

It answers the questions Where? When? How? In what manner? In what condition? or To what extent?

Examples:

• They moved the luggage of the guests to the room.

• The student lives in an apartment across the street.

The phrase to the room tells where the luggage was moved and in an apartment modifies the verb lives. These are adverbial phrases.

You can find a prepositional phrase anywhere in the sentence and sometimes you can find more than one prepositional phrase in a sentence.