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 then explains that prepositional phrases can function as adjectives or adverbs in sentences. As adjectives, they answer questions like "which one?" and as adverbs they answer questions like "how?" or "where?". It provides sentence examples to illustrate this. Finally, the document provides an exercise where the reader underlines prepositional phrases and circles what they modify in sample sentences.