Markdown is a "lightweight" markup language. The UBB tags used to format posts on FineTunedMac is an example of a Markup language. In other words a set of tags that define how the text should appear. Markdown is a bit simpler and generally requires only a single formatting symbol at the beginning of a line of plain text. For Example:
Quote:
click here
markdown on the left resulting PDF on the right

The advantage is it can be created using virtually any plain text editor and permits the author to focus on the content with only minimal formatting concern. The output format is the province of an interpreter and the results can be anything from formatted PDF to HTML code from the same markdown source. The actual format and final appearance is determined at compile or production time.

Markdown is widely used in software documentation and interpreters are built into diverse applications such as Python (programming language), Xcode (Software development environment), DEVONThink 3 (database system), and Scriviner (authoring system). After several trials, my favorite Markdown editor by far is iA Writer (it is NOT the cheapest).

If we knew what it was we were doing, it wouldn't be called research, would it?

— Albert Einstein