Entity classes represent table in database with its data members as a columns. To define a class as an entity we have to write an @Entity annotations above the class. Every table has a primary key like wise to define primary key in entity class we use @Id annotations above the data member to define the respective data member is primary of the table. Every entity classes must contain getters and setters to manipulate data. Some annotations used with entity classes: @Table(name="name") @Column(name="name") Relationship like(@OneToOne, @OneToMany, @ManyToMany, @ManyToOne) Example: https://github.com/adityakalambe01/Employee-Management-System/blob/main/src%2Fmain%2Fjava%2Fcom%2FEmployeeManagement%2Fentity%2FEmployee.java