[Q] what is mean posting-from-work-p in gnus-posting-style

[황병희]

Hellow, i am seeing Gnus manual [1]. At there is odd statement.

#+BEGIN_SRC emacs lisp
(setq gnus-posting-styles
      '((".*"
        (signature-file "~/.signature"))
       ((posting-from-work-p) ;; A user defined function
        (signature-file "~/.work-signature"))))
#+END_SRC

What does (posting-from-work-p) means?
Actually i did fail to read and understand...

Sincerely,

[1]https://www.gnu.org/software/emacs/manual/html_node/gnus/Posting-Styles.html

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