Shader.

Definition

A shader is a small program that runs on the GPU and computes, in parallel, the color of every pixel (fragment shader) or the position of every vertex (vertex shader) in a scene. Unlike CPU code, which runs sequentially, a shader executes thousands of times simultaneously — once per pixel — which makes real-time visual effects possible at 60 frames per second. On the web they are written in GLSL and reach the browser through WebGL or WebGPU, enabling textures, distortions and lighting that the DOM or 2D canvas cannot deliver.