<%= app_name(:human) %>

Describe the whole project in a few sentences to a few paragraphs, just as you would explain it to your fellow developer. What is it actually, what was it built for, who is using it, etc

See makandracards.com/makandra/48339.

Architecture and models

Give a quick overview of the few core models and how they interact. Do not go into detail – class documentation should be written atop the class file. Just impart the very basics to grasp the application model, so a new developer knows where to dive in.

Development

Describe how to get started with the project. Document employed 3rd party services and how to use them, how to start a development server – just about anything that a new developer needs to know.

Peculiarity X

Add a section for each special concept in the application, e.g. a CDN and what it is used for, that icons are rendered from a custom icon font and how to update it, that all posts are created from an importer, that there's a web UI and a JSON API and an embeddable component.

Make the reader aware of a peculiarity, but remember to keep it short. Details should be documented in the respective area.