This extension detects when user opens a Moera node (or other website that implements Moera REST API) and replaces the site interface with a special Moera web client - the one-page web application. The code of the client is downloaded from a remote host. The location of the client is configured in the extension preferences. Read more about the architecture and purpose of the Moera browser extension at http://moera.org/overview/browser-extension.html.