Honeycomb is the 3.0 version of the os which is optimized for devices with larger screens. The OS is also adding lots of functionality for developers to take advantage of when developing Apps and more.
Speculation of just exactly what devices will be able to use the new UI has been quailed a little with the recent post on the Android Developers Blog. It will be mainly used for larger screens on devices such as Tablets.
Read more on the Developers Blog Page
Android 3.0 (Honeycomb) is a new version of the Android platform that is designed from the ground up for devices with larger screen sizes, particularly tablets. It introduces a new “holographic” UI theme and an interaction model that builds on the things people love about Android — multitasking, notifications, widgets, and others — and adds many new features as well.
Besides the user-facing features it offers, Android 3.0 is also specifically designed to give developers the tools and capabilities they need to create great applications for tablets and similar devices, together with the flexibility to adapt existing apps to the new UI while maintaining compatibility with earlier platform versions and other form-factors.
Today, we are releasing a preview of the Android 3.0 SDK, with non-final APIs and system image, to allow developers to start testing their existing applications on the tablet form-factor and begin getting familiar with the new UI patterns, APIs, and capabilties that will be available in Android 3.0