iframe
Noun · Development · Origin: 1997
Definitions
An HTML element that embeds another HTML page within the current page — a page within a page. Once the backbone of web layouts (frames), now primarily used for embedding third-party content like YouTube videos, maps, and ads.
In plain English: A way to embed one web page inside another web page — like a picture frame, but instead of a photo it shows a live website. Used for things like embedded videos and payment forms.