Ok, after clicking around for 10 minutes I think I figured out what this is: it is a single-page WYSIWYG HTML editor with the ability to export either everything including itself, or just the HTML without the editor.

How is this useful? For quick writing and sharing of HTML files, but not the links, but the files themselves.

Very interesting,thank you.

The idea is you would write everything in the webpage, like. Google Doc. Then you can download that web page and share it with anyone anywhere and nearly everyone will be able to read it because it will open in a browser

Would I be able to store and edit this type of note on Google Drive? I like to keep documents in the cloud so I can access and edit them from anywhere, like Google Docs. But I don't think Drive can actually open html files, despite working entirely inside the browser.

On my dropbox, I was able to modify and share it on the web or apps. It was not saved.

When I opened html on the file app on my iPhone, js didn't run, so I could only see it

I don't think it's perfect in many ways.

By 'note' I guess they mean rich text editor.