You know that a preposition is always followed by a noun or a pronoun (object) which adds to its meaning. This object along with the preposition is called a prepositional phrase.

Examples:

• The lady in the front row is smiling mysteriously.

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

• The student lives in an aparment across the street.

In the first sentence, in is the preposition, front row is the object, and the is the article that points out the noun (object). So in the front row is a prepositional phrase.

Prepositional phrases can act as adjectives and adverbs as they give us information about nouns, pronouns, or verbs.