> a) I think it's a site for sharing codes.
It is useful to distinguish between git and github.
Git is a widely used distributed version control software.
Github is a popular web based repository (of primarily code) that uses git for version control.
> It's mostly for teams and organisations that all work on open source projects.
Github does not dictate how the code that you place in github should be licensed. However, if the code is placed in a public repository on github, anyone can view (and license permitting, fork) the repository (though this, by itself, does not grant any right to use the code).
|You're under no obligation to choose a license. However, without a license, the default copyright laws apply, meaning that you retain all rights to your source code and no one may reproduce, distribute, or create derivative works from your work.|
It is also possible to host private repositories on github, which can't be viewed by others; but this is a paid service.
> c) I don't think one person who works on their non-open-course application would have much desire to use github.
True. You may still want to use git, because it is a good version control system; version control is useful for single-person software which needs to be refined and maintained over a period of time.
> Are these right please?
Yes. Setting the default (--global) user name and email address is the right first step.