"A demo (demonstration) is a non-interactive multimedia presentation made within the computer subculture known as the demoscene. Demogroups create demos to demonstrate their abilities in programming, music, drawing, and 3D modeling. The key difference between a classical animation and a demo is that the display of a demo is computed in real time, making computing power considerations the biggest challenge. Demos are mostly composed of 3D animations mixed with 2D effects and full screen effects."
— Wikipedia description