Point a camera at its own monitor and the image contains itself containing itself: video feedback, the oldest trick in electronic visuals. Analog artists tuned those loops into galaxies and tunnels decades before GPUs.
Digital feedback keeps the previous frame as a texture and redraws it each frame slightly transformed (scaled, rotated, warped, faded) under the new content. Trails, infinite zooms, and the entire MilkDrop aesthetic are this one structure with different transforms.
Feedback is powerful because it is memory: the image accumulates history, so motion leaves wakes. It is also unstable by nature, brightening or dying without careful gain control, which is half the craft of using it live.