- https://git-scm.com
- https://git-scm.com/book – the online Pro Git book – quite a nice introduction (– and probably more than that)
what about GUIs?
- https://git-scm.com/downloads/guis
- https://git-scm.com/download/gui/linux – there are not just the “built-in GUI” tools
- https://git-scm.com/docs/git-gui – (“built-in”) GUI tool for committing
- https://git-scm.com/docs/gitk – (“built-in”) GUI tool for browsing
…