The difference between WebDriver and RemoteWebDriver in Selenium is as follows:-
WebDriver represents is an object which represents the browser in Selenium. Using that object you can control the Web browser.
WebDriver is an interface of the org.openqa.selenium.* package. Upon instantiating the implementations of this class the browser will be launched.
FirefoxDrive, ChromeDriver, InternetExplorerDriver, SafariDriver, OperaDriver, HtmlUnitDriver, RemoteWebDriver are few implementations of the WebDriver Interface.
RemoteWebDriver is the WebDriver object to control the desired browser in the node PC over the Grid using the Capability(settings) and Hostname or IP of the Selenium HUB running.
By using RemoteWebDriver object instantiation, you can control any browser in the node PC which is on Windows, Mac, Linux etc.. platforms.
Here is a Selenium Training Course that you can take up to learn it in a much better way. You can also watch the below-mentioned video-tutorial to learn WebDriver. .