WebDriver has a simple API designed to be easy to work with and can drive both real browsers, for testing javascript heavy applications, and a pure 'in memory' solution for faster testing of simpler applications.

For the 5 minute introduction, take a look at the GettingStarted page. For a more in depth introduction to WebDriver and various DesignPatterns that might be useful you may want to watch this GTAC presentation.

We release javadocs for the most recently released Java version of WebDriver. They are are available here.