A prepositional phrase is a group of words that begins with a preposition and ends with a noun or pronoun, known as the object of the preposition. This phrase provides additional information about time, location, direction, or manner. For example, in the phrase "under the table," "under" is the preposition, and "the table" is the object. Prepositional phrases can function as adjectives or adverbs in a sentence. For instance, in the sentence "The book on the shelf is mine," the phrase "on the shelf" describes which book. Similarly, in "She ran to the store," the phrase "to the store" tells us where she ran.