This document discusses prepositions and prepositional phrases. It defines prepositions as small words like "in", "on", "at" that come after a verb and before a noun. Sometimes prepositions are two words like "because of" or three words like "in addition to". A prepositional phrase is formed when a preposition is combined with a noun, such as "on the table". Prepositional phrases can indicate where something is, when something occurs, possession, or describe or identify someone or something. The document provides examples of different types of prepositional phrases and advises that prepositional phrases can be used at the beginning of sentences to vary writing style.