And Today, I have tried out their free trial version. The product is so intuitive and I was able to setup a custom font in no time. Also, I have taken a look at how it works. Basically, they ask you to include the JavaScript snippet as shown below in your web page where you require the custom font.
<script type="text/javascript" src="http://use.typekit.com/qip6nwu.js"></script>
<script type="text/javascript">try{Typekit.load();}catch(e){}</script>
This takes care of fetching the customized font that you have selected on Typekit website through a CSS file request. This CSS file makes use of the CSS @font-face feature(Read more about font-face here). The CSS response looks something like as shown below. They load the font through data URI instead of making another http request.
@font-face {
font-family:"league-script-no-1";
src:url(data:font/opentype;base64,d09GRk9......);
font-style:normal;
font-weight:400;
}
.tk-league-script-no-1{
font-family:league-script-no-1,sans-serif;
}
Now, use this CSS selector class(.tk-league-script-no-1) in your web page for the elements for which you need the customized font to be applied.