Shader
Also said as Fragment shader, Pixel shader, Vertex shader, GLSL, HLSL
A small program that runs on the graphics card, usually once for every pixel or corner of a model, in parallel. It decides position and colour, and that decides how everything looks.
A shader changes the whole look of a game without changing a single model. Each one also runs millions of times a frame, so one expensive line can use up the frame budget on its own.
Say it
“Write a toon shader for the characters: three flat light bands and a dark rim, so they read clearly against the painted backgrounds.”
Where you’ve seen it
Return of the Obra Dinn renders its scene in greys, then a post-processing shader compares each pixel with a tiling dither pattern to get its 1-bit look, as Lucas Pope set out in his dev log.
Not to be confused with texture
A texture is a picture stored in memory. A shader is the code that decides what to do with it.