So for instance, you can't use iframes to embed a YouTube video. (pressbooks.com)
It's a fairly simple operation to copy and paste a snippet of iframe code into your website; if that seems daunting, you can also opt for a link to a branded page. (realtormag.realtor.org)
An instance of the [HTML] script element included in an XHTML Content Document that is embedded in a parent XHTML Content Document using the [HTML] iframe element. (idpf.org)