From Wikipedia…
The demoscene is an international computer art subculture that specializes in producing demos: small, self-contained computer programs that produce audio-visualpresentations. The main goal of a demo is to show off programming, artistic, and musical skills.
The demoscene’s roots are in the home computer revolution of the late 1970s, and the subsequent advent of software cracking. Crackers illegally distributed video games, adding introductions of their own making (“cracktros“), and soon started competing for the best presentation.[1] The making of intros and standalone demos eventually evolved into a new subculture, independent of the gaming[2]:29–30 and software piracy scenes.
Demos in the demoscene sense began as software crackers‘ “signatures”, that is, crack screens and crack intros attached to software whose copy protection was removed. The first crack screens appeared on theApple II computers in the late 1970s and early 1980s, and they were often nothing but plain text screens crediting the cracker or his group. Gradually, these static screens evolved into increasingly impressive-looking introductions containing animated effects and music. Eventually, many cracker groups started to release intro-like programs separately, without being attached to pirated software. These programs were initially known by various names, such as letters or messages, but they later came to be known as demos.[4]