Markdown
Plain-text formatting that generates HTML. John Gruber + Aaron Swartz, 2004. **bold**, # heading, [link](url). De-facto standard for READMEs, docs, blogs.
The original spec was loose → many dialects (Pandoc, MultiMarkdown, GFM). CommonMark (2014) standardized the core; all modern parsers build on it. GitHub Flavored Markdown (GFM) added tables, strikethrough, task lists, automatic linking. Pandoc is the Swiss army knife for Markdown → 30+ formats. Aaron Swartz co-created — died 2013 in connection with the Reddit/JSTOR case.