The entire Pro Git book, written by Scott Chacon and Ben Straub. Link Here
Git and GitHub for Beginners - Crash Course. This course was developed by Gwen Faraday at the @FreeCodeCamp.org platform. Link Here
Markdown is a way to style text on the web. You control the display of the document; formatting words as bold or italic, adding images, and creating lists are just a few of the things we can do with Markdown. Mostly, Markdown is just regular text with a few non-alphabetic characters thrown in, like # or *.
You can use Markdown most places around GitHub:
- Gists
- Comments in Issues and Pull Requests
- Files with the .md or .markdown extension
Exemples here