In this article Icon Fonts refers to using the @font-face rule in #CSS to embed TTF, EOT and similar font formats into a web page. This is not an article about Cufón sIFR or any other method.
The entire purpose of using icon fonts is to replace the need to render icons on a web page using images. Icons fonts can be styled dynamically using CSS. They are smaller in file size than an image sprite. Being vector in nature, they are infinitely scaleable.