So BJ, the significance of these demos, is that they are technically, artistic and sonic challenges for the teams that develop them.
They have been around a LONG time, and predate a lot of the 3d games you've played. For example, if memory serves, FC released it's second reality demo in '92, which contains a component of these little engines flying around buildings and such. There was nothing, _NOTHING_ on the market that could even touch that level of 3d rendering back in the day (Descent came out in 95?)
so, as if the challenge wasn't enough, 3d morphing, refraction, raytracing, line drawing algorithms, complex reflections, the next step was to do it in the less code possible, hence the 4k and 64k competitions, meaning the compiled code had to come in under 64k.
I'll give you a minute to process that.