Internal frames

The page you are viewing is made up of traditional frames in the upper and right regions of the screen and an iframe in the center, where you're (probably) reading this content. While the traditional frames have been made obsolete in the current HTML specification, the iframe would still be considered good practice for the time being. Iframes allow for an experience that is similar in execution to frames, but is less likely to present problems in which third party websites get stuck inside someone else's digital cage. They may or may not be better for accessiblility when designing for screen readers in mind. (The best practice when designing for accessibility is to have static pages without dynamic content, or use server-side scripting to produce a static page, but that's outside the scope of this discussion.)

Internal frames are still used by many major companies to embed content on the web. They're how people place YouTube videos and Twitter feeds in their personal or professional webpages. There are discussions in the security community about the potential risks the widespread use of iframes poses, as with any technology that embeds third party content on a site, tracking and malicious scripts can end up on otherwise wholesome pages as a result of their misuse. (I absolutely promise that this iframe poses you no danger.)