Selenium IDE

• a Firefox add-on that you can only use in creating relatively simple test cases and test suites

Selenium Remote Control (RC)
”Selenium 1”

• the first Selenium tool that allowed users to use programming languages in creating complex tests

Selenium WebDriver

• the newer breakthrough that allows your test scripts to communicate directly to the browser, thereby controlling it from the OS level

Selenium Grid

• a tool that is used with Selenium RC to execute parallel tests across different browsers and operating systems