EJB3 mappedby

What does mapped by actually do

@Entity
public class Cubicle implements Serializable {
    private static final long serialVersionUID = 1L;
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name="CUBICLE_ID")
    private Long id;

    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }
    private Employee residentEmployee;

    @OneToOne(mappedBy = "assignedCubicle")
    public Employee getResidentEmployee() {
        return residentEmployee;
    }

    public void setResidentEmployee(Employee employee) {
        this.residentEmployee = employee;
    }
}

CREATE TABLE APP.EMPLOYEE (
    EMPLOYEE_ID BIGINT GENERATED ALWAYS AS IDENTITY(START
WITH 1, INCREMENT BY 1) NOT NULL,
    ASSIGNEDCUBICLE_CUBICLE_ID BIGINT,
    CONSTRAINT SQL090228015516800 PRIMARY KEY(EMPLOYEE_ID)
)
GO
ALTER TABLE APP.EMPLOYEE
    ADD CONSTRAINT MPLYSSGNDCBCLCBCLD
 FOREIGN KEY(ASSIGNEDCUBICLE_CUBICLE_ID)
 REFERENCES APP.CUBICLE(CUBICLE_ID)
GO

CREATE TABLE APP.CUBICLE (
    CUBICLE_ID BIGINT GENERATED ALWAYS AS IDENTITY(START
WITH 1, INCREMENT BY 1) NOT NULL,
    RESIDENTEMPLOYEE_EMPLOYEE_ID BIGINT,
    CONSTRAINT SQL090228015517160 PRIMARY KEY(CUBICLE_ID)
)
GO
ALTER TABLE APP.CUBICLE
    ADD CONSTRAINT CBCLRSDNTMPLYMPLYD
 FOREIGN KEY(RESIDENTEMPLOYEE_EMPLOYEE_ID)
 REFERENCES APP.EMPLOYEE(EMPLOYEE_ID)
GO