Which difference between them is like and this is the system of checking versions. Why in some cases used git and in the other github.

Answer 1, Authority 100%

If rude and in a nutshell:

Git is a program that monitors versions. It makes the repositories that need to be stored somewhere.

GitHub is a website where you can store repositories created in Git

Therefore, the phrase “in some cases is used and in the other GitHub” – incorrect. Even when github is used to store the repository, Git is still used to manage this repository.

That is, it is still like asking – why people to search for information sometimes use Google.com search, and in other cases – Google Chrome browser.