This framework should simplify creation UITableView based forms of data (e.g. your app settings screen, an object details/editing screen etc.). These forms must be fully animatable and provide easy way to customize visual appearance by supporting styles.
Preferences.framework located at /Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS4.2.sdk/System/Library/PrivateFrameworks/Preferences.framework. This is the most closed component by this time and I've tried to guess what it does internally. See Basics of Preferences.framework.