Systems comprise the entire interaction's backing stack. They are made up of Devices, Platforms, and Surfaces.
A device is any physical hardware involved in an interaction system. Devices support Platforms and include any peripherals involved in Surfaces.
Platforms are software used to process interactions. Surfaces interface with Platforms behind the scenes.
Surfaces are any ways which the user can perform interactions. These can be buttons, microphones, knobs, etc. Surfaces interact with the Platform running on the Device to complete the interaction.
Products are any software which the user's device hosts solely or primarily for the user. These include Web browsers and any downloadable software. The user is able to continue using discontinued Products.
Services are any software which someone else's device hosts for the user. These include all online applications. If the Service is discontinued, the user is no longer able to use it.