Downloading and Using Google Earth
To use Google Earth, you'll first need to download it. Go to the Google Earth website and click on the download tab to get started. The standard version of Google Earth is free, but they also offer a Pro version for businesses at a pricetag of $399 with a few extra features, such as ones for making movies and spreadsheets, and an "Enterprise" version for even higher-end business use that doesn't actually have an official price, but instead asks you to contact Sales, which probably translates to "expensive." Still, for businesses that are going to be using the extra features, both the Pro version and the Enterprise version are worth a look. The free version is more than enough for the casual user, however.
Once you've downloaded it, start up the program. It will give you a few helpful tips at startup, and I do recommend reading through those before you dive right in, because they give a brief explanation of some of the helpful tools. At any rate, once you're past that, you're ready to get started.
Navigation works very similar to how it does in Google Maps. First, you can rotate the map by clicking and dragging the compass in the top right, and you can use the tools underneath to move and zoom. You can also use the mouse to drag the map or zoom with your mouse wheel, just like in Google Maps. And, just like in Google Maps, there are street view images available if you zoom in all the way to the ground, at least in a city where there are streets for there to be images of.
All of the images in Google Earth, with the exception of the streetview images, are taken using satellite imagery, and there are some very interesting tools beyond simple navigation to allow you to see and learn a lot of different things.