As explained in the documentation about how PieCrust works, the page contents that you write go through a formatter before the page is rendered or baked. PieCrust ships with 2 standard formatters: Markdown and Textile.
The formatter used on a page is determined by the format setting in the
page’s configuration header:
* `markdown` for Markdown
* `textile` for Textile
If unspecified, the extension of the page file is matched against the
site/auto_formats setting in the site configuration:
* `.md` for Markdown
* `.textile` for Textile
Otherwise, the site/default_format setting in the site configuration will be
used, and that’s Markdown by default.
For a list of valid formatter names, see the formatters reference.