Recently I took a great introductory course to Git/GitHub from Udacity. Those of you who are interested in what Git and GitHub is or simply want to add a better structure to your knowledge, please, follow this link. Here I decided to post a cheat sheet with some basic commands and a bit of theory behind them that I learned from that course.
git init
git init should be executed when you are located in your working directory. When you initialize a repository, Git creates a hidden folder named .git. This folder keeps track of all the history and changes that have ever been done to your files.