Markdown is a text-to-HTML conversion tool for web writers. Markdown allows you to write using an easy-to-read, easy-to-write plain text format, then convert it to structurally valid XHTML (or HTML). Thus, “Markdown” is two things: (1) a plain text formatting syntax
Ever needed to test some markup or CSS for how it renders? Typically it's a tedius process of creating a HTML file, saving it, and then viewing it in a browser.