A browser extension is a small software program that adds specific features or functionalities to a web browser, such as blocking ads, managing passwords, or enhancing privacy. These add-ons are installed directly into browsers like Chrome, Firefox, or Edge, allowing users to customize their browsing experience. While browser extensions can improve convenience and productivity, they can also pose security risks if malicious, potentially allowing hackers to steal data or monitor user activity. It is important to only install extensions from trusted sources and regularly review their permissions.