An iframe can be a convenient way of including external content inside of a page. It works similar to the traditional frameset tag with one major difference. In the case of an inline frame (iframe), you can include this extra content directly within the body of your page.
The external content that you are calling shows up as a container set to the size that you determine anywhere you insert the iframe html code. The iframe element cannot be resized by the end user, so be sure that you set your height, width, and scrolling attributes to allow for a good user experience.
It is helpful to know that search engines and some older browsers cannot "see" the iframe content, so you should be sure to provide an alternative description of the content you are including between the iframe tags. Browsers that do not support the iframe tag will render this instead and search engine spiders are able to index this content.