The Copper List is a program consisting of display instructions executed by the Amiga's dedicated Copper co-processor, which runs in lockstep with the video raster beam. It enables mid-frame modification of custom chip registers to achieve hardware-driven effects like color cycling, gradient backgrounds, and screen splitting without CPU overhead. Each instruction typically waits for a specific screen position before writing values to registers such as color lookup tables or scroll offsets, effectively allowing time-based programming of the display hardware.