matchfix operator declaration



Dear developers,

I wonder if I can reformulate  the following  part of Rules.texi:
@code{matchfix (@var{ldelimiter}, @var{rdelimiter}, @var{arg_pos}, @var{pos})} 
declares the argument part-of-speech @var{arg_pos} 
and result part-of-speech @var{pos}, 
and the delimiters @var{ldelimiter} and @var{rdelimiter}.

what is "part-of-speech" here?  Is it just a "class" of arguments and results?
Can I just say  
"declares matchfix operator with the argument kind of  @var{arg_pos} 
and result kind of  @var{pos},and the delimiters @var{ldelimiter} and 
@var{rdelimiter}"?
There is no examples in the manual as well

Cheers
Valery