An IFrame (Inline Frame) is an HTML document which is placed in another page of a website. One of their main uses is to import quickly and easily content from a different source into the “recipient” page. Typical examples include adverts or banners – in fact, they act in essence in the same way as an image, albeit that they are capable of being amended to operate apart from and distinct to the scrollbar of the page in which it is placed. Many mortgage lenders, brokers and others supply IFrames to affiliates to populate their on-page application forms. See an example here at http://www.blueskyloans.co.uk.
An IFrame can be altered without the need to reload the page in which it is embedded.
Installation is straightforward. The relevant code is simply copied and pasted into the host web page. You can see how it is done in the video below: