How to use Dillinger web-based Markdown editor

Dillinger is a cloud-enabled, mobile-ready, offline-storage compatible, AngularJS-powered HTML5 Markdown editor.

Markdown is a lightweight markup language based on the formatting conventions that people naturally use in email. As John Gruber writes on the Markdown site

The overriding design goal for Markdown's formatting syntax is to make it as readable as possible. The idea is that a Markdown-formatted document should be publishable as-is, as plain text, without looking like it's been marked up with tags or formatting instructions.

This text you see here is actually written in Markdown! To get a feel for Markdown's syntax, type some text into the left window and watch the results in the right.