The document discusses prepositions and prepositional phrases. It defines prepositions as words or phrases that show the relationship between a noun or pronoun and other words in a sentence, often indicating location, direction, time, or other relationships. It then provides examples of common prepositions like about, above, across, after, below, along and phrasal prepositions like according to, across from. It asks the reader to identify prepositions and write sentences using specific prepositions in certain positions.