"Shader" is a dedicated program for vertex operations within a 3D plane (coordinate transformations relative to the vertex, light source calculations by vertices, etc.), and pixel operations (light source calculations for and coloring of pixels, etc.) In Unity, the Shader consists of Surface Shader, Vertex Shader, and Fragment (pixel) Shader. From Unity 4.0 onwards, Compute Shader has been available for usages in other purposes (such as GPGPU and so on).