The openGL ES 2.0 have a programmable graphic pipeline and this is due to the shader.
How are the shader the responsible of the programmability of openGL ES 2.0 graphic pipeline?
I’m not sure I understand your question.
Shaders are programs that run on the graphics core to process vertex, texture and other scene data. Under OpenGL ES 2.0 there are vertex shaders that are run per vertex and fragment shaders that are run per pixel.