With the media browser a user can upload, delete and modify files. You can open the media browser at
Right top account menu > Media. The media browser is also available as a popup throughout the system.
Each user has his or her own folder. Don't use the media browser for sensitive data, because files residing in it can be accessed by the web. For example, it's used to manage images which are shown in the app. And thus have to be accessed by an external source.
robots.txt file it's possible to prevent search engine crawlers to index the files, but that's no guarantee they are not found.