This is the Header Document in your Website Portal. It´s a sticky on top of everything else you publish in here. To edit it, simply open it, delete this text, and start writing... 

By default, the Portal behaves like a Blog: if you drop documents or messages into it, they will appear below the Header, sorted by date.
 
Initially, the Portal is not in use. You can choose between using the Portal Container as your website Homepage - or using the Homepage Document. Switch between them by changing Homepage Mode in Layout Properties. You can also change the Portal´s behaviour in its Layout Properties. For example to give it a different Blog Format, or make it a Media Collection.
 
Using the Portal container makes it possible to put together a Homepage combining many different elements.