Case is a way of indicating the role of a noun or pronoun in a sentence. There are three kinds of cases in English Grammar; they are subjective, objective, and possessive case.
Noun or pronoun used as a subject in a sentence is called a subjective case.
Example: He is smart. Harry is playing. She is beautiful. They are going to a party. The Child is singing a song. (In the above example sentence he, Hari, she, they, and the Child is used as subjective case.)
Noun or pronoun used as the object of a verb is called an objective case.
Example: She eats bread. He teaches Lucy. The gift is for you. The cat drinks milk. He came from the London. (In the above example sentence bread, Lucy, you, milk, and London are used as objective case.)
Noun or pronoun used to express ownership is called a possessive case.
Example: Sofia is his sister. The book is mine. The suitcase is hers. She is John’s mother. Dany’s car is imported. (In the above example sentence his, mine, hers, John’s, and Dany’s are used as possessive case.)