Markdown is a language that anyone can make good use of if you write material that has to be formatted in any of a number of ways, but without the downside of using a word processor (which is likely to mess up your material) or writing detailed code (like HTML or whatever you’d have to do to make a PDF file). (I’ve written about it here: What is Markdown and why use it? and How to blog: Text Workflow on an iMac)
It was invented nearly ten years ago by John Bruber and Aaron Swartz. Gruber called Markdown “A text-to-HTML conversion tool for web writers. Markdown allows you to write using an easy-to-read, easy-to-write plain text format, then convert it to structurally valid XHTML (or HTML).” but it also converts to PDF and other formats.
Instant Markdown is a book by Packt Publishing that gives a complete and concise tutorial and overview of the language. The book is brief but complete (Markdown is not that complex). It provides information on how to install it, gives all the details there are on how to use it, and provides a few pointers and references to useful resources.
Markdown is easily used form the command line on any system (if you have the right stuff installed) but is even easier to use on a Mac if you install something like “Marked.” In this case you use a text editor and Marked. As you write a .txt file and update (save) it, Marked shows you the results as it will appear on a web page or PDF file (more or less) and optionally shows the raw HTML code, which you can then copy and past. Markdown is used in several existing platforms and there are on line sites where you can put your markdown and get back formatted text. Those on line sites and the blogging platforms, etc., that use markdown language are described in the book. If you are going to mess with markdown, this is a good guide.