guide - Tcl "primitives" or "extensions"

[markd at macports.org]

>if everything  necessary to write portfiles, including standard TCL, were
> 
>documented in the guide and/or the manpage.

Some questions:

1) So is the portfile manpage not exhaustive, and if not what is missing? 
Or do I have to mine the base code for an exhaustive list?
2) The manpage calls them "Tcl Extensions" -is that the best term or is
"Tcl primitives" better?

Mark