For y'all non-programmers, don't be scared by the term “API.” In non-programmer terms, what this announcement means is that any web designer or developer—or, indeed, anyone who can edit the HTML and CSS of their own web pages—can now use high-quality free fonts in their web pages, by adding one line of HTML code and one line of CSS.
To try out a super-easy example yourself, see the getting started page.
This is cool for all sorts of reasons. For one thing, a lot of the text that web designers usually embed in images can now be displayed as plain text, which often means faster load times, and almost certainly means better maintainability and accessibility. It also means you can apply all sorts of CSS styling to that text—for example, you can add subtle drop shadows with one line of CSS.
I've changed the entry titles in my blog to use a fancy open source font called “Tangerine”; I may end up changing them to something else at some point, but if you're reading this entry elsewhere and want to see how it looks, stop by my blog.
But again, you don't need to be super-technical to use the Font API itself. Just don't get carried away in filling up your page with lots of fonts; follow good design principles.