In Pictures: Mozilla previews app store in time fo...
Prism, the predecessor to Firefox apps
Firefox apps appear to be based on the premise of Mozilla’s Prism, which is no longer being developed by them. It allowed you to install a web link as an application shortcut on your computer’s OS. Clicking such a shortcut would launch a stripped down version of Firefox (minus its standard GUI), which in turn would go to the URL and load the web-based app (or page) at the address. Chrome has a similar feature built into it.
In Pictures: Mozilla previews app store in time for the holidays