A technology demo is a prototype, rough example or an otherwise incomplete version of a product, put together with the primary purpose of showcasing the idea, performance, method or the features of the product. They can be used as demonstrations to the investors, partners, journalists or even to potential customers in order to convince them of the viability of the chosen approach.

Computer technology demos should not be confused with demoscene-based demos, which, although often demonstrating new software techniques, are regarded as a stand-alone form of computer art.

Fakes

Occasionally, technology demos prove out to be rigged or even completely fake. For example, an empty case with some blinking LEDs can be presented as the product, a demo of Internet QoS software can be done on a LAN with manually-regulated traffic, and a pre-rendered video or pictures with notably higher-quality models or resolution can be presented as actual game footage. This last example happens so often in the game industry, it has earned the nickname bullshot.

"Any sufficiently advanced technology is indistinguishable from a rigged demo." - Andy Finkel

See also here.