Hi:

         When we use <c-]>,sometime it will prompt:

         nr pri kind tag                  file

           1 F         f    mch_delay                os_amiga.c

                            mch_delay(msec, ignoreinput)

           2 F         f    mch_delay                os_msdos.c

                            mch_delay(msec, ignoreinput)

           3 F         f    mch_delay                os_unix.c

                            mch_delay(msec, ignoreinput)

         Enter nr of choice (<CR> to abort):

         (h tag-matchlist)

         What the ‘f’ means?

         Sometimes it is ‘n’,’c’,’r’ or ‘p’.what those means?

         Where can we found it’s help?

The ctags documentation probably has details on kind; it is contained in the generated tags file. I'm not sure whether Vim does anywhere.

    ctags --list-kinds

If you are interested in the kinds of only one language, you can
specify that, too, as this example for C:

    ctags --list-kinds=c

To see the list of languages supported, execute

    ctags --list-languages

For more help, use

    ctags --help | less

Regards,
Gary