Neat reference, going to look into that.
The <object> tag appears to include/embed other html pages.
An embedded HTML page:
<object data="snippet.html" width="500" height="200"></object>
https://www.w3schools.com/tags/tag_object.asp
<object> used like this is just a poor iframe in a much shakier spot in the standards, mostly for backwards compatibility.
Like iframe, it "includes" a full subdocument as a block element, which isn't quite what the OP is hinting at.
Yeah, that is just a crappier version of HTML Frames [1]
1 - https://en.m.wikipedia.org/wiki/Frame_(World_Wide_Web)
<object> used like this is just a poor iframe in a much shakier spot in the standards, mostly for backwards compatibility.
Like iframe, it "includes" a full subdocument as a block element, which isn't quite what the OP is hinting at.