PhantomJS is a headless web browser scriptable with JavaScript, used for automating web page interaction. Being headless means it operates without a graphical user interface, which makes it faster and more efficient for tasks like web scraping, web testing, and site automation. PhantomJS can render web pages, handle user interactions, and execute JavaScript, allowing for the extraction of dynamically generated content. It is particularly useful for scraping websites that heavily rely on JavaScript to display data. Although PhantomJS has been discontinued, it remains a valuable tool for certain web scraping tasks.