About `remote-tty'

[Xue Fuqiao]

In (info "(elisp) Process Information"):

 -- Function: process-tty-name process
[...]
     If PROCESS represents a program running on a remote host, the
     terminal name used by that program on the remote host is provided
     as process property `remote-tty'.

What does "process property" mean here?

It seems that it's not an overlay property or a text property, maybe
it's a symbol property.  I've used `M-x apropos', searched the archives
and manuals, but nothing helped.  I'd like to read the source code, but
I'm not familiar with process.c.

-- 
Xue Fuqiao
http://www.gnu.org/software/emacs/