A computing device that provides predefined services, and that has its underlying operating (OS) software hidden beneath an application-specific interface. Computing appliances offer reduced complexity (e.g., installation, administration and maintenance) and faster deployment by hiding the operating software and embedding the application within the device. A computing appliance may be based on a general-purpose OS (e.g., Windows, Solaris or Linux) if the OS’s complexity is hidden and the ability to load arbitrary services is removed.

Computing appliances can provide one or more services; however, they not general-purpose devices in that they are not flexible in the services they provide. Administrators do not need platform expertise — just limited application and appliance-specific expertise.

Gartner has defined four fundamental types of computing appliances — see separate entries for server appliance, storage appliance, network appliance and client appliance.