Prism is a simple browser that hosts web applications in a very basic interface. It can be used to free up your normal browser of open tabs or pages, by loading web applications such as Gmail, Facebook or Twitter in separate Prism pages.
The advantage is that Prism is not affected if your browser ever crashes. It also allows you to keep your favorite web applications open in a separate window.
One of the major advantages of Prism is probably that it uses up very little memory, around 20 MB when we tested it with Facebook.
Of course though, don't expect yourself to find anything fancy in Prism.
No controls, panel bar or preferences, Prism is just a plain old window to load web apps. Similarly it won't support most of the features you take for granted in your browser, such as spell-checking or pop up window management.