How to Use iFrames for Facebook Apps
To offer apps on your business page, you will quite possibly need to do as much building off Facebook as you would on Facebook. Page tabs are blank spaces provided by Facebook in which you input an app URL that Facebook then displays through a simple web interface called an iframe. This means that much or all of your content isn’t on Facebook — it’s simply viewed through a window.
An iframe allows an HTML browser window to display the contents of practically any web page inside another. In a Facebook page tab, this feature means that you, the app creator, can create your own content on your own web server, and display that content inside a nicely polished Facebook interface right on Facebook.com itself. The iframe is a box inside your page that displays content from your own website.
To set up your page tab, go to Facebook’s app builder, create your app, and specify the URL on your website that you want Facebook to load in your Facebook page. Install the app on your page, and — voila! — the content in the page is loaded every time your fans visit the app on your page.
For example, you can see and use the Post Planner app right inside Facebook by using http://www.postplanner.com/ as the URL for your page tab. After the foundation of your app is built in Facebook, an iframe allows you to display any content on the web.