Shader
A small program that runs on the GPU for every corner or every pixel at once.
See it in Shader forge. Pick the Plasma preset, then change a number in the code and watch the picture update.
In plain words
A shader is a short program that runs on the graphics chip. One kind runs for every corner of a shape and decides where it lands on screen. Another runs for every pixel and decides its colour. Because the chip runs thousands of copies at the same time, a whole screen can change every frame. Almost every moving picture in the lab is drawn by shaders.