Markdown is a markup language that's meant to be simple and readable no matter what. Even as plain text, Markdown looks as good as when it's parsed and formatted. HTML can be used inside Markdown documents for advanced functionality (AutoSite still requires the attribute declarations in Markdown, for example).
AutoSite supports the semi-canonical CommonMark implementation; any Markdown files (text files with the .md extension) in your pages folder will get built into proper HTML documents. If you're mostly writing plain text with some light formatting (say, for a personal blog), you can use Markdown to speed up the process and save yourself some serious typing.
[#] Creating a Markdown Document
To create a new Markdown document, in the Sitemap, right click on the folder you'd like to create the document in, hover the "New" submenu, and select "Markdown Page (.md)". Type the name of the file and double-click it to bring it into the Code Editor.
[#] Learning Markdown Syntax
If you're interested in using Markdown for your site's pages, thankfully, Markdown is remarkably simple to learn. John Gruber's original Markdown description is simple, if not exhaustive, and CommonMark maintains a spec, a cheat sheet, and a tutorial.In the spirit of this manual as a demonstration piece for AutoSite, this page in particular has been written as much as possible in Markdown; you can view the original page source here.