This application runs in the status bar and displays a list of items stored in your Reading List (from iCloud). This allows you to open the items in your default browser rather than only from Safari.
In order for this application to work on your Mac, you must have an iCloud account with Bookmark syncing enabled. You iOS device will also require an iCloud account with booking syncing enabled if you want to add to the Reading List from iOS and read them on your Mac. This is necessary as the app does not communicate with iCloud; it reads Safari's Bookmarks file but it doesn't change this file.