A Markdown is a simplied and user friendly method to code/stylize webpages in the Github environment.
What are some examples of Markdowns?
Text Manipulation with *, such as enclosing text in 2 asterisks will make it bold
Text Size Manipulation via #, such as preceding any text with 1-6 Hashtags will determine the size it displays on your page. 1 hashtag being largest and 6 hashtags smallest.
There are features for advanced users such as Syntax Highlighting that uses Java Script