From http://msdn.microsoft.com/en-us/library/windows/apps/xaml/hh768232.aspx :
“The Split App template is a great way to start creating a Windows Store app that you can customize to enable users to view a list of items and item details in a two-column view, where users might want to switch quickly among the items, and where the list might be updated dynamically. Examples include a news reader, a sports scores app, or an email app.
The Split app starts with a home page that shows a list of groups. A group is a named set of items, like a news source that provides news stories. When the user selects a group by tapping or clicking it, the app opens the split-view page. “
The difference between this app and the Grid App is that there are only two pages. The main page only shows the groups and the second page lists the items in the selected group (without any details about the selected group). The second page shows the selected item as chosen from the item list on that page. The data is the same for both apps.
This application has the following .xaml pages as well as code behind page (ie .cs) for each: