The MARKDOWN extension is used in files storing text which is code written in the MARKDOWN markup language. This language allows you to easily format text and convert such documents to HTLM or XHTML format. The MARKDOWN file also makes it possible to easily read the text itself in a file written in that language.

The MARKDOWSN markup language was developed by John Gruber and Aaron Swartz. It uses simple tags, e.g. the notation "