To get more information about any git command – i.e. details about what the command does, available options and other documentation – use the --help option or the help command.
For example, to get all available information about the git diff command, use:
git diff --help
git help diff
Similarly, to get all available information about the status command, use:
git status --help
git help status
If you only want a quick help showing you the meaning of the most used command line flags, use -h:
git checkout -h