Markdown is a markup language. The name is a pun, but where the humor might be atrocious, the language is not. The Markdown language lets you write plain text documents with a few lightweight annotations that specify how you want the document formatted. Such annotations are the defining characteristics of a markup language. Markup languages separate the semantic or content part of a document from the formatting of said document. The content of a document is the text, what should be headers, what should be emphasized, and so on. The formatting specifies the font and font size, whether headers should be numbered, and so on.
Markup languages have a stronger focus on semantic information than direct formatting as you would do with WYSIWYG (what you see is what you get) formatting. With markup languages, you might annotate your text with information about where chapters and sections start, but not how chapter and heading captions should be formatted. Decoupling the structure of a text from how it is visualized makes it easier for you to produce different kinds of output. The same text can easily be transformed into HTML, PDF, or Word documents by tools that understand the markup annotations. And because writing the text and formatting it are separate steps, you can apply one or more text documents to the same transformation program to get a consistent look for related documents, or you can transform the same document into multiple output formats so the same document can be put on a web page or in a printed book, for example. Most WYSIWYG editors can export to different formats, but they usually do not let you output to the same document type with different formatting, for example, output PDF files in A4, 6˝ x 9˝, and 7˝ x 10˝ with point size 11 in the first two and 12 in the last. With a Markup language, this is relatively easy.
Among markup languages, Markdown is one of, if not the, simplest. The annotations you add to a text are minimal, and most likely you will already have seen most of them if you occasionally use plain text files. For example, where you would use italic or boldface in Word, you would write *italic* and **boldface** in Markdown, and most likely you have seen this notation before. In my misspelled youth, I frequently used TeX/LaTeX and HTM-L/SGML/XML. I know people who cannot concentrate on the text body if it is full of markup information. With Markdown, the markup annotation is almost invisible, and they have no problem working with that. With Markdown you can generate documents in other markup languages, so you do not need to know them. If you want the full power to format your documents the way you want them, then I still recommend that you learn the other languages. You can use that knowledge to create templates (see Chapter 9), and then you only need to use, for example, LaTeX or HTML when writing the templates. You can then still keep your document in Markdown. One exception, where you still want to use LaTeX, is if you need to write math in your document. Then you need to write it in LaTeX; see Chapter 6.
You need a program for translating Markdown into other file formats. The tool I will use in this book is Pandoc. Pandoc supports basic Markdown and several different extensions. It also lets you define templates and stylesheets to customize the transformed files. Pandoc can do more than translate Markdown files into different output files. It can translate from and to several different formats. I will only describe how you translate from Markdown to other formats. If you have an existing text in Word, for example, and you want to try out Markdown by editing that document, then you should be able to generate a Markdown file from the Word file, edit the Markdown format, and then translate the Markdown document back to Word.