It presents an interface which is divided into 4 pieces:
- HTML editor
- CSS editor
- and the output
You can select the framework & the version of your choice (MooTools, jQuery, Dojo, Prototype, YUI, Glow,Vanilla). Also, if there is, you can add a complimentary framework like jQuery UI or MooTools More.
A great feature is the ability to save & share the code created with a unique URL generated. Optionally, jsFiddle has an embedding feature too.
What would be better is the ability to select multiple JS frameworks at the same time (also having a server-side file & an editable database would make it a complete playground).