Service Workers are scripts that run in the background of a web browser, separate from a web page. They enable features like offline access, background syncing, and push notifications, enhancing the user experience. Service Workers act as a proxy between the web application and the network, allowing developers to manage how requests are handled. To use a Service Worker, a website must register it, which typically occurs when the page loads. Once registered, the Service Worker can intercept network requests and cache responses, making it possible for users to access content even without an internet connection.