What is a BasePage class in POM? Why do you need it?

// BasePage.java
public class BasePage {
    protected WebDriver driver;
    protected WebDriverWait wait;

    public BasePage(WebDriver driver) {
        this.driver = driver;
        this.wait   = new WebDriverWait(driver, Duration.ofSeconds(15));
    }

    // ── Element interactions ───────────────────────────────────────

    protected void click(By locator) {
        waitForClickable(locator).click();
    }

    protected void type(By locator, String text) {
        WebElement el = waitForVisible(locator);
        el.clear();
        el.sendKeys(text);
    }

    protected String getText(By locator) {
        return waitForVisible(locator).getText().trim();
    }

    protected String getAttributeValue(By locator, String attr) {
        return waitForPresent(locator).getAttribute(attr);
    }

    protected boolean isDisplayed(By locator) {
        try {
            return driver.findElement(locator).isDisplayed();
        } catch (NoSuchElementException e) {
            return false;
        }
    }

    // ── Wait utilities ─────────────────────────────────────────────

    protected WebElement waitForVisible(By locator) {
        return wait.until(ExpectedConditions.visibilityOfElementLocated(locator));
    }

    protected WebElement waitForClickable(By locator) {
        return wait.until(ExpectedConditions.elementToBeClickable(locator));
    }

    protected WebElement waitForPresent(By locator) {
        return wait.until(ExpectedConditions.presenceOfElementLocated(locator));
    }

    protected void waitForInvisible(By locator) {
        wait.until(ExpectedConditions.invisibilityOfElementLocated(locator));
    }

    protected void waitForTextInElement(By locator, String text) {
        wait.until(ExpectedConditions.textToBePresentInElementLocated(locator, text));
    }

    // ── Navigation ─────────────────────────────────────────────────

    protected void navigateTo(String url) {
        driver.get(url);
    }

    protected String getCurrentUrl() {
        return driver.getCurrentUrl();
    }

    protected String getTitle() {
        return driver.getTitle();
    }

    // ── Scroll ────────────────────────────────────────────────────

    protected void scrollToElement(By locator) {
        WebElement el = driver.findElement(locator);
        ((JavascriptExecutor) driver).executeScript("arguments[0].scrollIntoView(true);", el);
    }

    protected void scrollToBottom() {
        ((JavascriptExecutor) driver).executeScript("window.scrollTo(0, document.body.scrollHeight);");
    }

    // ── Dropdown ──────────────────────────────────────────────────

    protected void selectByText(By locator, String text) {
        new Select(waitForPresent(locator)).selectByVisibleText(text);
    }

    protected void selectByValue(By locator, String value) {
        new Select(waitForPresent(locator)).selectByValue(value);
    }

    // ── Screenshot ────────────────────────────────────────────────

    protected void takeScreenshot(String name) {
        File src = ((TakesScreenshot) driver).getScreenshotAs(OutputType.FILE);
        try {
            FileUtils.copyFile(src, new File("screenshots/" + name + ".png"));
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

// LoginPage.java
public class LoginPage extends BasePage {
    // Locators
    private By emailInput    = By.id("email");
    private By passwordInput = By.id("password");
    private By loginBtn      = By.cssSelector("[data-testid='login-btn']");
    private By errorMsg      = By.className("error-msg");

    public LoginPage(WebDriver driver) {
        super(driver);   // calls BasePage constructor
    }

    public DashboardPage login(String email, String password) {
        type(emailInput, email);          // BasePage method
        type(passwordInput, password);    // BasePage method
        click(loginBtn);                  // BasePage method
        return new DashboardPage(driver);
    }

    public String getError() {
        return getText(errorMsg);         // BasePage method
    }
}

// DashboardPage.java
public class DashboardPage extends BasePage {
    private By welcomeMsg = By.cssSelector("h1.welcome");
    private By logoutBtn  = By.id("logout");

    public DashboardPage(WebDriver driver) {
        super(driver);
    }

    public boolean isWelcomeDisplayed() {
        return isDisplayed(welcomeMsg);   // BasePage method
    }

    public LoginPage logout() {
        click(logoutBtn);                 // BasePage method
        return new LoginPage(driver);
    }
}