You can store your personal files inside the box. These files are available as normal server (or NAS device), over the WebDAV protocol and of course via the browser.
As example you can synchronize your photos from your smart phone (e.g. with Folder Sync) automatically onto your box.
Another use case is the back up of your social media apps, which can be copied automatically onto you box. Or the sharing of document with one of you main customers.