[html5] "internal slot"

[Gomer Thomas]

       Thanks for the response.
        I found the statement "We use the notation x@[[y]] to refer to
internal slots of an object", but I could not find a definition of what an
"internal slot" is. What am I missing?
       Regards, Gomer Thomas
       --
       Gomer Thomas Consulting, LLC
       9810 132nd St NE
       Arlington, WA 98223
       Cell: 425-309-9933
       
       -----Original Message-----
From: Domenic Denicola [mailto:d at domenic.me] 
Sent: Monday, April 11, 2016 3:25 PM
To: Gomer Thomas <gomer at gomert-consulting.com>; help at lists.whatwg.org
Subject: RE: [html5] "internal slot"
       
       It is defined in https://streams.spec.whatwg.org/#conventions.