iFrames are third party applications that can be embedded on a site. Commonly used example include Google maps, Youtube and Spotify.
To embed Youtube, Vimeo videos or Google maps, drag and drop the icon from the add panel on the left and replace the embed code by clicking on the <iframe> blue icon on the top left of the map.
For other iframes, drag & drop an empty iframe component from the left add panel.
Then, replace the code by clicking on the blue <iframe> icon on the top left of the element.