Google Experience Device
A product that is backed by Google but manufactured by another company. For example, the Motorola Xoom tablet is made by Motorola, but it has pure Google Android operating system installed with no extra fluff and applications that you cannot easily get rid of.
Google simply does not have the manufacturing resources to manufacture the products themselves, so Google "outsources" the manufacturing to companies with the explicit contract not to add any fluff-ware.
Google Experience Device = Pure Android, 100% Google.
List of Google Experience Devices: (In order of release)