–help option gives a short description about using any command when typed in the terminal followed by the particular command in which you need help. Following example shows the use of rmdir command.
rmdir –help (press enter)
Usage: rmdir [OPTION]… DIRECTORY…
Remove the DIRECTORY(ies), if they are empty.
ignore each failure that is solely because a directory
-p, –parents remove DIRECTORY and its ancestors; e.g., `rmdir -p a/b/c’ is
similar to `rmdir a/b/c a/b a’
-v, –verbose output a diagnostic for every directory processed
–help display this help and exit
–version output version information and exit