The biggest change in Selenium recently has been the inclusion of the WebDriver API. Driving a browser natively, as a user would, either locally or on a remote machine using the Selenium server, marks a leap forward in terms of browser automation.
Selenium WebDriver fits the same role as RC did, and has incorporated the original 1.x bindings. It refers to both the language bindings and the implementations of the individual browser controlling code. This is commonly referred to as just WebDriver or sometimes as Selenium 2.
Selenium 1.0 + WebDriver = Selenium 2.0
WebDriver is designed in a simpler and more concise programming interface along with addressing some limitations in the Selenium-RC API.
WebDriver is a compact object-oriented API compared to Selenium 1.0.
It drives the browser much more effectively and overcomes the limitations of Selenium 1 that affected our functional test coverage, like the file upload or download, pop-ups, and dialogs barrier.
WebDriver overcomes the limitation of Selenium RC’s single-host origin policy.