Not too long ago, web designers were restricted to a set of universal type faces that were installed on nearly every computer. If they wished to use more extravagant typographical designs, they pretty much always had to create images with them instead of directly placing the text on the page.
With the @font-face CSS rule, designers can input their own fonts on websites, not relying on the visitor to have the font already installed. In a design community where there are literally hundreds of thousands of free fonts available, having the freedom to use any font you desire is like taking blinders off of a horse.
Keep in mind the rules of design however. More than three fonts on one page is going to look excessively busy, and will likely slow down the loading times of your site. Designmodo helps walk designers through adding the @font-face CSS rule, and they urge everyone to use universal fall back fonts, which is smart advice. Not every browser supports @font-face, and you don’t want to ruin accessability for any group of users.