Hello Nitin, GeckoDriver is a web browser engine which is used in many applications developed by Mozilla Foundation and the Mozilla Corporation. GeckoDriver is the link between your tests in Selenium and the Firefox browser. GeckoDriver is a proxy for using W3C WebDriver-compatible clients to interact with Gecko-based browsers. In order to instantiate the object of GeckoDriver, you can simply create the object with the help of the below command.
Webdriver driver = New FirefoxDriver();