The framework is mainly aimed for iOS enabled devices.
It comes with 3 base modules.
The Base Module is a simple template that let's the developer build up the styles from the ground up.
It has some basic styles, like headers, buttons, and some other elements.
This is recommended for building a custom User Interface and will not be using any iOS UI elements.
The iPhone Elements Module is a CSS3 file made by Jeff Broderick and is aimed at replicating some of the iOS native UI elements.
Using some simple classes developers will be able to create seamless iOS experiences on the web.
The jQueryMobile Module uses the jQuery Mobile framework.