Markdown is a lightweight markup language that adds formatting such as headings, lists, links, and code blocks to plain text using simple syntax. It was created by John Gruber in 2004.

It is widely used for developer-oriented documentation including GitHub READMEs, technical blogs, and documentation sites (MkDocs, Docusaurus). Standardization specifications include CommonMark and GitHub Flavored Markdown (GFM). Technical writing guides cover Markdown usage extensively.

Markdown's advantage is that it remains readable as plain text while being easily convertible to HTML. However, complex formatting like tables and footnotes varies in support across dialects.

From a character count perspective, Markdown syntax characters (#, *, [], etc.) are not displayed, creating a difference between source character count and rendered character count. Documentation best practices books provide additional insights.