https://seleniumhq.github.io/selenium/docs/api/java/index.html
HtmlUnit Driver
This is currently the fastest and most lightweight implementation of WebDriver. As the name suggests, this is based on HtmlUnit. HtmlUnit is a java based implementation of a WebBrowser without a GUI. For any language binding (other than java) the Selenium Server is required to use this driver.
WebDriver driver = new HtmlUnitDriver();
I tried it, there is no gui interface , but it can be tested normally, but there will be css warnings.
Other drivers are not outlined. FirefoxDriver(), ChromeDriver(), InternetExplorerDriver () , etc. have interfaces, all of which open the corresponding browser.
iosDriver and android's Driver
Reference URL:
http://ios-driver.github.io/ios-driver/
http://selendroid.io/