Git

• distributed version-control system for tracking changes in source code during software development
• works for any text-based files
• can be accessed via commandline (git bash) or graphical interface (git GUI)

Github

• a web-based service for version control with git
• has a GUI for ease of use
• including features like "issues", that are independant of git
• alternative Plattforms:
  • GitLab: allows also private repositories in free plan
  • BitBucket: another competitor