Markdown is a simple text-to-HTML converter that turns common text idioms into HTML. The full syntax is available from the author's site, but here's a short summary:

• Paragraphs: Start a new paragraph by skipping a line.
• Italics: Put text in italics by enclosing it in either * or _: *italics* turns into italics.
• Bold: Put text in bold by enclosing it in two *s: **bold** turns into bold.
• Pre-formatted text: Enclosing a short block of text in backquotes (`) displays it in a monospaced font and converts HTML metacharacters so they display correctly. Example: `<img src="foo"/>` displays as <img src="foo"/>. Also, any paragraph indented 4 or more spaces is treated as pre-formatted text.
• Block quotes: Any paragraph (or line) that starts with a > is treated as a blockquote.
• Hyperlinks: You can create links like this: [amazon's web site](http://www.amazon.com). That produces "amazon's web site".
• Lists: You can create numbered or bulleted lists by ending a paragraph with a colon (:), skipping a line, and then using asterisks (*, for bullets) or numbers (for numbered lists). See the Markdown syntax page for examples.
• Raw HTML: Markdown will pass raw HTML through unchanged, so you can use HTML's syntax whenever Markdown doesn't provide a reasonable alternative.