G - stands for Git (or TFS, SVN, even CVS, which are all source / version control systems).

Git is a system for tracking changes to source code - sas, html, css, js, xml, etc. It is also a workflow for change management and integration testing, supported by vendor platforms such as Github, Gitlab, Bitbucket and more.

Typical git commands include:

git clone "some repo" - create a new local copy of a remote git repository

git branch BRANCHNAME - create a new branch (eg for building a new feature in isolation)

git checkout BRANCHNAME - switch to a different branch

git pull - get the latest version of the current branch from the remote repository

git status - scan ALL files in the repository to see which have been changed, and which are staged

git diff SOMEFILE - compare the changes of a particular file to the last commit

git add SOMEFILE - stage a file for commit

git commit -m "SOME MESSAGE" - commit staged files with a commit message.

When written properly, commit messages can be used to auto-generate release documentation and semantic version numbers - the article below is well worth a read.

https://www.conventionalcommits.org/en/v1.0.0-beta.3/