Pixel shaders are programs that run on the GPU to manipulate pixels. There are different types of shaders including pixel shaders, vertex shaders, and geometric shaders. Shaders replaced fixed functionality with programmability, allowing effects to be programmed. Popular shader programming languages include HLSL, GLSL, and Cg. Cg is a C-like language designed for GPU programming and shader development. It allows shaders to be written in a high-level language and compiled for different GPUs.