kyle, Iframes work very much like how normal frames work, cept iframes are floating frames. Meaning you can put an Iframe anywhere, for example in a table cell. You can give the iframe a Name="frame1" and have your links or forms Target="frame1", like how you would do regular frames.
Iframes are a great new feature in webbrowsers. You can put anything you want in the Src attribute. Any url you can dream of can be used.
Iframes work in IE5+ and Netscape 6+ . If any of your projects require you to use earlier versions then iframes wont be available. Netscape 4 did have a Layer Tag, But was pretty useless compaired to iframe.