Selenium is a powerful open-source tool primarily used for automating web browsers, making it ideal for testing web applications across different platforms. It supports multiple programming languages such as Python, Java, C#, and JavaScript, allowing developers to create scripts that can interact with web pages by simulating user actions like clicking, typing, and scrolling. Selenium works with various browsers, including Chrome, Firefox, and Edge, by using specific WebDriver executables for each. It offers flexibility in locating webpage elements through methods like ID, name, class, CSS selectors, and XPath. Selenium also handles dynamic content through implicit and explicit waits, ensuring scripts sync properly with page load times. Its integration with testing frameworks like PyTest or JUnit allows for effective validation of test results. This makes Selenium an essential tool for creating efficient, automated, and reliable tests that mimic real-world user behavior, greatly improving the overall quality and robustness of web applications.