Markdown is a lightweight markup language that is used for formatting plain text documents. It is designed to be easy to read and write, and is often used for creating web content, such as blog posts, documentation, and readme files. Markdown is popular because it is simple to learn and use, and is easy to convert into HTML and other formats. It is also used for creating rich text in a variety of applications, such as email, text editors, and the web. Markdown supports many features, such as lists, links, code blocks, italic and bold text, and more. It is often used in combination with other tools, such as Git, to create a powerful and efficient workflow.
Discontinued The program seems to be no longer updated. The latest version, 2.5, released in December 2014, can still be downloaded from the official website.
Asciidoctor provides a much more advanced syntax than Markdown when you need it, but it is still just as simple if all you are writing is a basic document. In other words, the extra features are there when you need them, which saves you from having to migrate to a different system. It also provides a very nice styling of the generated HTML right out of the box. Unlike Markdown, it can produce much more formatting than just HTML.
Most powerful and complete markup language.
Free, Real-time editing, File synchronization from Dropbox, drive, etc. Very good.