The Placemark Window is where you can customize your placemark and how it is displayed. You can set the title, the geographic coordinates and the icon. Turning on the "Show Title" checkbox will have the placemark always display its title.
The Description field can contain plain text, HTML styled text or even the URL of a website or image.
The zoom slider on the right side of the city window enables you to customize the maximum camera elevation that the placemark icon will show at. Click the "+" or "o" label to start setting the maximum elevation. Once you click that button, the button will change to an "x" and your camera will center on your placemark. To set the zoom, move the camera in or out to the desired level and click the "x" button. You can remove the maximum elevation setting from the placemark by clicking on the "-" button.