The document discusses the use of possessive case in English grammar. It provides 7 cases or rules for using possessive case, including with plural nouns ending in "s", compound possessives, double or triple possession, and omitting the possessed object when it is understood. It also notes the use of possessive case with expressions of time and when personifying places. There are examples provided for each case or rule. Finally, there is an exercise that asks the reader to transform sentences into possessive case.