1. Selenium Integrated Development Environment (IDE)
2. Selenium Remote Control (RC)
4. Selenium Grid
Selenium is a suite of tools that helps in automating only web applications. You should have a basic understanding of Java or any other object-oriented programming language for using Selenium.It has capabilities to operate across different browsers and operating systems.
Selenium IDE -a Firefox plugin that lets testers to record their actions as they follow the workflow that they need to test.
Selenium RC-was the flagship testing framework that allowed more than simple browser actions and linear execution. It makes use of the full power of programming languages such as Java, C#, PHP, Python, Ruby and PERL to create more complex tests.
Selenium WebDriver-is the successor to Selenium RC which sends commands directly to the browser and retrieves results.
Selenium Grid-is a tool used to run parallel tests across different machines and different browsers simultaneously which results in minimized execution time.