bash - How do I know the exact and complete Linux whereis command search path

Reading the man pages about the "whereis" command on my Debian 'wheezy' linux, it shows that the file interested are:

FILES
   /{bin,sbin,etc}
   /usr/{lib,bin,old,new,local,games,include,etc,src,man,sbin,
                           X386,TeX,g++-include}
       /usr/local/{X386,TeX,X11,include,lib,man,etc,bin,games,emacs}

I assume that those are the hard-coded search paths, but why I get this:

root@kali:/bin# whereis gnome
gnome: /usr/share/gnome
root@kali:/bin#

Why does it show it? Since it is not not on the assumed path?

... and moreover it is a directory, not a binary, source or manual.