An ad blocker is a software or browser extension that prevents advertisements from being displayed on a webpage or app. It works by filtering out the code and content that is responsible for displaying ads, effectively shielding the user from unwanted and often intrusive marketing messages. Ad blockers provide a seamless and uninterrupted browsing experience, allowing users to focus on the content they are interested in without being bombarded by distracting ads. They are a popular tool for improving online privacy and reducing data usage, as well as enhancing the overall user experience.