Icing is a structured editor, designed to create content for the web without having to write HTML.
The content is fully editable from a visual editor and is stored as simple JSON. It can be then converted to HTML, or also be tweaked as it is displayed, with additional elements interweaved or alterations made depending on the context.
I have written some more thoughts on Icing on my site.
The building blocks of an Icing document (subsections, blocks, and traits) can all be customised using a Specs file.
Icing can load any custom Specs files, allowing you to create your own particular structure and formatting. These can also be shared for anyone to use.
The Specs format is in-progress. You can see an example Specs JSON file here: http://burnticing.github.io/specs/default/1.0/default-1.0.json