Google Earth is an extension of Google Maps. While Google Maps is a web application Google Earth is a Windows desktop application. When you start Google Earth you see the earth globe, which grows gradually and zooms in on USA. You can change your view manually by pressing the left mouse button and rotating the globe in any direction you want. As you fall towards earth you begin to see city markers “New York”, “London”, “Hamburg” … You also see that patches of the globe are colored in different shades of gray. That’s the regions where satellite pictures are available. The brighter the shade the better the quality.
That looks nice, but that’s not where it ends. Zoom in on some city in the USA, say New York. Now below the map view, you’ll find some checkboxes. One of them is “buildings”. Select this one and you’ll see how Google Earth will paint bright cuboids over most of New Yorks satellite picture. Also below the map view to the right of the cursor key pad you’ll find a tilt slider. Tilt the view till you literally stand on one of the streets of New York. Now all of those cuboids create a 3D model of New York. Some of them are smaller, some are taller. It looks really realistic - the cuboids only lack their real textures. Now you can take a walk on the Broadway, fly through New York like Spider Man or what ever.
Google Earth is a really cool toy. The satellite pictures outside the USA are a bit sparse and not as good as the ones from USA, but this will most likely change. It’s a very fascinating feeling when you fall towards earth and just with the wink of a hand change your destination.