At its simplest you can think of World Wind as a desk globe, however World Wind is not a simple desk globe.
World Wind allows any user to zoom from outer space into any place on Earth. World Wind leverages satellite imagery and elevation data to allow users to experience Earth terrain in visually rich 3D, just as if they were really there. Virtually visit anyplace in the world. Look across the Andes, into the Grand Canyon, over the Alps or along the African Sahara.
Unlike your desk globe World Wind can display thousands of placenames all over the world, from Country capitals to villages in sparsely populated regions. You can see country borders, and in some cases intracountry borders such as US states.
World Wind can also be expanded to include additional imagery and data. There have already been a number of add-ons created, from Norway's Prehistoric Hillforts to additional planets.