Markdown has been made a markup language of choice by many different platforms including the one I use often: Github, Atlassian Jira, Stack Exchange. The language was designed to be readable as-is, without looking like it's been marked up with tags or formatting instructions (unlike HTML). Since its initial development in 2004 by John Gruber’s there have been number of efforts attempting to standarise it. John's own Perl script converting Markdown into HTML has been used as the initial definition for Markdown but since it has number of ambiguous definitions causing issues, many different standards of the language emerged. The differences are mainly around more advanced features thought and the base is rather common and this is what I'm going to concentrate on here. Also there is an inititiative called CommonMark (commonmark.org) describing itself as a strongly specified, highly compatible implementation of Markdown, with many popular individuals involved that standarises the language.