Google's Street View technology adds a degree of realism to Google Maps by allowing you to view most roads as if you are actually standing on them. Google uses a vehicle mounted panoramic camera system to capture these images, providing complete panoramic views of any place the Google Street View vehicle has been to.
You can switch Google Maps into Street View mode by continuously zooming in on an area until the camera automatically switches to Street View mode, or by dragging the orange Pegman icon above the zoom bar on the left side of the screen onto a road. Street View data is available for any roads that are outlined in blue. Click the Street View image with your mouse and drag to change your perspective on the image. When the cursor becomes a square, you can double-click to zoom in on that part of the image. When it becomes a circle, you can double-click to move the camera. Alternately, you can click on the arrows in the road to move the camera down the street.
Google Street View is an excellent planning device. If you are attempting to find your way to a new place, you can use Street View to locate landmarks on the side of the road before driving there. Drag the Pegman to each of the major turns on your route to see what the area looks like so you can avoid missing your turn. Street View is also helpful for planning a pedestrian or bicycling route. Drag the Pegman to parts of your route to confirm that there is a bike lane or a sidewalk present. You can also use Street View to help decide where to take a vacation. Street View features data from all over the world, allowing you to virtually scout a location before actually deciding to go there.
Google is only legally allowed to collect Street View information and images for public places. In order to allow private property owners to showcase their property, Google has created a partner program by which a private property owner can invite Google to their property. The images from the property will then become available with the general Street View images. You can invite Google to your property using the partner program invitation on the Google Maps webpage.
As of Google Earth 6, you can access Google Street View data in Google Earth. Navigation in Google Earth is the same as navigation in Google Maps. Google Earth adds the benefit of countless other high definition satellite, aerial and ground photographs along with other information that is relevant to the area that you are viewing. You can toggle between Street View and 3D ground view by turning Google Earth's "3D Buildings" checkbox on and zooming out of Street View. This will give you a very similar view to Street View but rendered in 3D with detailed buildings in most urban areas.
In order to create Street View style images of indoor spaces, Google has shrunk their Street View technology down to a single trolley. They have used this trolley to capture images from the inside of museums around the world so you can tour foreign museums in Street View without leaving your computer. You can find more information about which museums are available at Google's Art Project site and you can visit the museums through Google Street View in Google Maps.