Selenium automates browsers. It is primarily used for automating web applications for testing purposes.
Selenium has the support of some of the largest browser vendors who have taken (or are taking) steps to make Selenium a native part of their browser. It is also the core technology in countless other browser automation tools, APIs and frameworks.
"Selenium 2 Testing Tools: Beginner's Guide" will help you begin with testing web applications using Selenium from scratch. From setting up the Java environment to running tests on mobile devices, it contains all the information to get a novice up and running on using Selenium.
You will also learn some advanced concepts such as testing complex web applications and running tests in parallel towards the end of the book.