Для чего нужен Page Object Pattern

public class LoginPage {
    private WebDriver driver;

    @FindBy(id = "username")
    private WebElement usernameField;

    @FindBy(id = "password")
    private WebElement passwordField;

    @FindBy(id = "login-button")
    private WebElement loginButton;

    public LoginPage(WebDriver driver) {
        this.driver = driver;
        PageFactory.initElements(driver, this);
    }

    public void login(String username, String password) {
        usernameField.sendKeys(username);
        passwordField.sendKeys(password);
        loginButton.click();
    }
}