The Live documents tile shows you an overview of the recent edited documents from the account you are logged in with. This gives users the option to open the file with the Online or Local Office Apps as well as opening the file location. As well as Share link and Attach to email. At the bottom you can also open the Documents app.
To activate the app:
Change the tile format to 4 x 4 to get live version.
When changed back to 2 x 2 or 1 x 1 format it will show the regular icon.