Github is simple to use and powerful git repository with great web interface. If your project is open source, there is no problem if your repository is also open, right? What could be better to open source projects than having free hosting on feature rich and reliable service?
But if you are not the good guy and want to have your git repositories private, looks fair to charge you little money to keep your code safe.
This looks to be the basic business model do Github and the prices are attractive.
For those have never being in touch with versioning and code repositories, Github is also good place to start. The step-by-step documentation will guide you over the process of using git. It is really easy to start.
Github also encourages you to make friends and to grow your social network around the code you share. I would like to be your friend on GitHub, so you are invited to see my profile: https://github.com/petersenna
If you are looking for a job, Github can also help you. You can make your "Job Profile" and select: "Available for hire". The link to your code looks to be that your "open" code repositories are your portfolio.