It should be used for fetching and caching resources for later user navigation as per the official HTML5 spec (i.e. prefetching a css file to be used in a page which highly likely to be used by the user in his upcoming navigation). Supported in Chrome, Firefox & IE.
It should be used for prerendering a complete page that the user will highly likely navigate to it in his upcoming navigation (i.e. like prerendering the next article where it is highly likely that the user will click on “next article” button). Supported only in Chrome & IE.