Computer graphics are graphics created using computers and, more generally, the representation and manipulation of image data by a computer.
What is Shader?
A shader is a small program or set of algorithms that determines how 3-D surface properties of objects are rendered, and how light interacts with the object within a 3-D computer program. NewerGPUs calculate shaders where previously it was an algorithm calculated by the CPU.
Shaders are simple programs that describe the traits of either a vertex or a pixel. Vertex shaders describe the traits (position, texture coordinates, colors, etc.) of a vertex, while pixel shaders describe the traits (color, z depth and alpha value) of a pixel.
As the major graphic software library: OpenGL, DirectX 3D, they provide three type shaders: vertex, pixel and geometry shader.
More detail: http://en.wikipedia.org/wiki/Shader
What is rendering?
Rendering is the process of generating an image from a model, by means of computer programs. The model is a description of three-dimensional objects in a strictly defined language or data structure. It would contain geometry, viewpoint, texture, lighting, and shading information.
What is Shading?
In computer graphics, Shading refers to the process of altering a color based on its angle to lights and its distance from lights to create a photorealistic effect. Shading is performed during the rendering process.
What is RenderMonkey?
It's a shader development IDE.
