Markdown is a markup language. It is the de facto (unofficial) standard for writing READMEs for programs, and many programs can convert markdown documents into richtext.
# Heading 1 ## Heading 2 ### Heading 3 Alternative heading 1 ===================== Alternative heading 2 --------------------- **bold**, *italicized* > blockquote 1. List item 2. List item 3. List item - List item - List item `code` --- - horizontal rule [Link](http://a.com) [Image](http://a.com/image.png) or [Image](image.png)