Selenium is a widely used open-source framework for web UI automation testing, known for its compatibility across various browsers, platforms, and programming languages such as Java, Python, and C#. The tutorial delves into the intricacies of Selenium WebDriver, a core component of Selenium that facilitates browser automation by acting as a bridge between the test framework and web browsers. It highlights the evolution of Selenium from separate projects to a unified framework and discusses the enhanced features of Selenium 4, including W3C compliance, improved Grid setup, and relative locators. While Selenium WebDriver offers numerous advantages like supporting multiple OS and browsers, it also has limitations like lacking built-in reporting and Windows application automation. The guide provides a detailed walkthrough of setting up Selenium WebDriver with Eclipse and demonstrates executing automated tests using both local and cloud Selenium Grids, emphasizing the benefits of cloud-based solutions like LambdaTest for parallel testing.