Selenium is a tool that helps you interact with browsers to test your software's user interface. It does not run tests directly on the software itself, but rather performs tasks based on commands given to it. Selenium should be used as part of a broader testing strategy, focusing on its role as a UI investigative tool during the code testing phase of the software development lifecycle. The overall testing automation journey is more complex and multi-faceted than using just one tool like Selenium. Understanding Selenium's limitations helps developers create a more effective testing approach.