Quote - A shader is the material of an object. Color, gloss, texture, bump and displacement maps and so on. In short, the surface...

Shaders tell the render engine how the light interacts with the surface also, more advanced shaders can add things like curves which are like ribbons (think of hair and fur).

There are some amazing things that can be done using shadermixer, helps if you have a maths background so you can understand what the bricks do better but it can be fun to just play in there sometimes. (If I can do it anyone can...my maths is minimal.)

IIRC these were created using shadermixer...

 

edited to add...just love the renders. When I get some cash I must get these...