We are now ready to use Selenium. Selenium was written by Jason Huggins in 2004 while working at ThoughtWorks. It is not just a single tool, but a suite of tools, that allows you to automate browsers across multiple platforms. We will be using the JavaScript binding to Selenium WebDriver, but it's beneficial for us to take a quick look at each part of the tool suite:

• Selenium Remote Control (RC), also known as Selenium 1.0, is the first tool in the suite that allows you to automate browsers. It works by injecting JavaScript scripts into the browser when the page is first loaded. These scripts would simulate user interaction by clicking on buttons and inputting texts. Selenium RC has been deprecated and is superseded by Selenium WebDriver.
• Selenium WebDriver, also known as Selenium 2, is the successor of Selenium RC, and uses the standardized WebDriver API to mimic user interaction. Most browsers have built-in support for the WebDriver API, and so the tool doesn't need to inject scripts onto the page anymore.
• Selenium Server allows you to run your tests on a remote machine, such as when using Selenium Grid.
• Selenium Grid allows you to distribute your tests over multiple machines or virtual machines (VMs). These tests can then run in parallel. If your test suite is large, and/or you need to run tests on multiple browsers and/or operating systems, then test execution is likely to take a long time. By distributing these tests across multiple machines, you can run them in parallel and reduce the total execution time.
• Selenium IDE is a Chrome extension/Firefox plugin that provides a rapid prototyping tool for building test scripts. Essentially, it can record actions a user takes on a page, and exports them as a reusable script in many languages. A developer can then take this script and further customize it to their own needs.

For testing our application, we are going to be using Selenium WebDriver.