Markdown is a specific markup language designed to produce HTML output. You can find the specification for Markdown
here and a Markdown cheatsheet
here. Virtually any plain text editor can be used to create Markdown source code, however a list of Markdown tools will be found
here.
A
markup language is a document formatting language and there are literally hundreds of markup languages. Wikipedia has a reasonably comprehensive list of markup languages
here. The best known markup language is probably HTML and there are any number of WYSIWYG (What You See Is What You Get) editors for HTML such as Pages, Sparkle, Flux, Hype, and as many as 95 more listed in the App Store alone, not to mention non-WYSIWYG editors such as BBEdit and its free sibling TextEdit.
The BBCode used on FineTunedMac is a lightweight markup language whose output, like Markdown, is a subset of HTML that is recognized in browsers.