Markdown is a lightweight markup language created by John Gruber in 2004 for writing formatted text using plain-text editors. It's designed to be easy to read and write, converting seamlessly to HTML while remaining human-readable in its raw form. Markdown has become the de facto standard for documentation, README files, note-taking apps, static site generators, and content management systems. The CommonMark specification standardizes Markdown syntax, while GitHub Flavored Markdown (GFM) extends it with tables, task lists, strikethrough, and autolinks — features now widely adopted across platforms.