You spend half or more of your waking life staring into them, but what are they, how do they work and just how different are they?

An explanation of the North Korean mass games: https://www.koryogroup.com/travel-guide/travel-guide-north-korea-mass-games

A 25 inch e-ink monitor: https://goodereader.com/blog/electronic-readers/onyx-boox-mira-pro-is-a-25-inch-e-ink-monitor

Holographic display: https://www.youtube.com/watch?v=-EA2FQXs4dw