Markdown is a lightweight markup language. Lightweight Markup Languages (LML) are those that are simplier and more human readable than, for example, HTML. Lightweight markup languages are used in applications where it may be necessary to read the raw document as well as the final rendered output.
Markdown is often used to in Content Management Systems (e.g. Drupal, etc.), to format readme files, in online discussion forums, and to create rich text using a plain text editor.
Markdown was created by John Gruber and Aaron Swartz in 2004. Gruber received his Bachelor of Science in computer science from Drexel University. Swartz attended Stanford University and was posthumously inducted into the Internet Hall of Fame in 2013 after passing away on January 11 of that year.
Swartz was a programmer, entrepreneur, writer, political organizer, and Internet hacktivist. He was involved in the development of the web feed format RSS, Markdown language, the organization Creative Commons, creator of the website framework web.py, and was co-founder of the social news site Reddit. In 2010, he became a research fellow at Harvard University's Safra Research Lab on Institutional Corruption.
You can run markdown a variety of ways: