What Do the Experts Say? FreeBSD (10.3)

• man rm (excerpts slightly re-arranged):

     The rm utility attempts to remove the non-directory type files specified
     on the command line.  If the permissions of the file do not permit writ-
     ing, and the standard input device is a terminal, the user is prompted
     (on the standard error output) for confirmation.

     -d      Attempt to remove directories as well as other types of files.

     -R      Attempt to remove the file hierarchy rooted in each file argu-
             ment.  The -R option implies the -d option.

     -r      Equivalent to -R.

     -f      Attempt to remove the files without prompting for confirmation,
             regardless of the file's permissions.