The document discusses the proper uses of the apostrophe in grammar. It outlines three main uses of the apostrophe: 1) to form possessive nouns, 2) to indicate contractions, and 3) to form the plural of certain words. The document provides examples for each of the three main uses and guidelines for applying apostrophes correctly, such as with plural vs. singular nouns, nouns ending in "s", and possessive pronouns vs. contractions.