Apple has released another update for iTunes after having just released version 10.2 last week. It is not clear why such an update was required so soon and there were no differences listed on the release notes.
iTunes 10.2.1 was released with new Java builds for Mac OSX Leopard and Snow Leopard and the update could be just for some minor bug fixes. The update has the same features as 10.2, which added iOS 4.3 and Home Sharing support to sync with iPhone, iPad, and/or iPod Touch.
Support for iOS 4.3 and Home Sharing will allow you to stream music from a PC or a Mac to an iOS device. However, iOS 4.3 will not be available until March 11th along with the iPad 2.