General commands for getting help and/or documentation for command line utilities in terminal on macOS?
Have you heard of using the man command. For example: man ls or man grep. You can get comprehensive documentation on man by entering man man.
Some of the basic keys used by the man command are the f key to page forward, the b key to page backward and the q key to quit.
Try using the mouse to highlight the command, then right click on the highlighted text and select Open man page. See example below.


Note: The highlighted text can not contain spaces.

Some commands are builtin. This means the command is part on the current shell. If you are using the zsh shell (which is the macOS default shell), then you will need to enter man zshbuiltins for documentation.