This article explains how to delete the history of an application in Windows 8. The Delete History can be helpfull but if the application history is not good for security and user privacy then you can delete it.
In Windows 8 when you close a Metro application then it is pushed rather then completely closed as like resume. This allows the user to switch among applications without launching the application. Using the Delete History you can delete all Metro application history and as well as exit from an application that is running in the background.
How to Delete application history in Windows 8
Move cursor on write-button and click on "Setting".
From Setting click on "Change PC setting".
From Change PC setting click on "General".
From the General window click on "Delete History".