This page offers a brief overview of what it's like to use Markdown. The syntax page provides complete, detailed documentation for every feature, but Markdown should be very easy to pick up simply by looking at a few examples of it in action. The examples on this page are written in a before/after style, showing example syntax and the HTML output produced by Markdown.
It's also helpful to simply try Markdown out; the Dingus is a web application that allows you type your own Markdown-formatted text and translate it to XHTML.
A paragraph is simply one or more consecutive lines of text, separated by one or more blank lines. (A blank line is any line that looks like a blank line -- a line containing nothing spaces or tabs is considered blank.) Normal paragraphs should not be intended with spaces or tabs.
Markdown offers two styles of headers: Setext and atx. Setext-style headers for <h1> and <h2> are created by "underlining" with equal signs (=) and hyphens (-), respectively. To create an atx-style header, you put 1-6 hash marks (#) at the beginning of the line -- the number of hashes equals the resulting HTML header level.
Blockquotes are indicated using email-style '>' angle brackets.
Markdown uses asterisks and underscores to indicate spans of emphasis.