Gecko Driver 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 i.e. Mozilla Firefox in this case. As Selenium 3 will not have any native implementation of FF, we have to direct all the driver commands through Gecko Driver. Gecko Driver is an executable file that you need to have in one of the system paths before starting your tests. Firefox browser implements the WebDriver protocol using an executable called GeckoDriver.exe. This executable starts a server on your system. All your tests communicate to this server to run your tests. It translates calls into the Marionette automation protocol by acting as a proxy between the local and remote ends.
