Seems like you have an Android tablet without the Google APIs. This are devices that use Android but without a Google branding ("with Google (TM)") and Google Services Framework (Google API) to avoid paying fees to Google. Android itself is open-source so every manufacture can use it without charge on their devices, but if they want to have the Google Services like Market, Maps, Navigation, Google Calendar and so an, they have to pay a license fee to Google. You can recognize devices with Google Services based on the "with Google (TM)" branding on the back of the device.
AFAIK there a ways to install the Google API when you have root on your device.