Git is a tool used to organize projects, commonly used for version control. Projects can be hosted on websites to allow multiple people to work on them. Github is the most popular website that uses Git. Both Git and Github are very complicated and in-depth, but most of the work common users will be doing is fairly surface-level.
Github has their own set of resources to help new users find their way around the site and become familiar with its tools.
A Git interface is usually what you will be interacting with while working on a project. I suggest using Git Bash (Windows-only) or just Git for people familiar with using a console, and Github Desktop for people who are used to Gui based programs.
Git also has resources for new users, which are useful for people using the console application and also provides a base level of knowledge to people using Github Desktop.