The document discusses prepositional phrases. It begins by defining a prepositional phrase as starting with a preposition and ending with a noun, pronoun, gerund, or clause. It provides examples of basic prepositional phrases like "at home" and "from Richie". The document notes that prepositional phrases usually function as adjectives or adverbs in a sentence. It provides examples to illustrate this and warns not to mistake the object of a preposition for the subject of the sentence. The document concludes by underlining prepositional phrases in sample sentences.