[plt-scheme] What is an embedded editor?

Way back on Aug 3, 2007, at 04:02, Robby Findler wrote to Grant Rettke  
and the list:
> Things like the XML boxes are embedded editors. Try typing this:
>
>  Special|Insert XML box.
>  <a href="http://www.google.com">
>  Special|Insert Scheme box
>  (string-append "Go" "og" "le")

When I Ran the experiment, I got:

(a ((href "http://www.google.com/")) "Google")

That looked great, but I was curious what behind the scenes code  
generated this, so I looked at the source after I saved the file.  I  
could barely read the decorated [ #reader(lib"read.ss""wxme")WXME0108  
##  ] source in Emacs, so back in DrScheme I did Save Other / Save  
Definitions as Text..., which was now:

<a href="http://www.google.com/">(string-append "Go" "og" "le")</a>

which cannot be Run:   reference to undefined identifier: <a

I think I was expecting to find something that could still be Run,  
like this:

`(a ((href "http://www.google.com/")) ,(string-append "Go" "og" "le"))