I have seen some embed codes provided as <interaction> tag. For instance, Apester's so-called HTML5 embed code goes like this
<interaction id="57b6f819336e03ca34e0fb8b"></interaction>
I have seen this with other providers of embed codes before (well at least once), but I can't find anything on this tag, not at W3C, WHATWG or MDN. I am wondering, what is this, how does it work and where can I read about it?
It's not standard, but a custom tag from Apester. Their javascript library (or sdk) will see it and use it. For more info, see this link.