See http://www.khw.s.org/on the official website,
OpenGL ES 1.x
For fixed function hardware: OpenGL ES 1.1 is defined relative to the OpenGL 1.5 specification and emphasizes hardware acceleration of the API, but is fully backwards compatible with 1.0. it provides enhanced functionality, improved image quality and Optimizations to increase performance while loading cing memory bandwidth usage to save power. the OpenGL ES 1.1 extension pack is a collection of optional extensions added to OpenGL ES 1.1 that extends CED variability and bring significant improvements in image quality and performance. learn more...
OpenGL ES 2.x
For programmable hardware: OpenGL ES 2.0 is defined relative to the OpenGL 2.0 specification and emphasizes a programmable 3D graphics pipeline with the ability to create shader and program objects and the ability to write vertex and fragment shaders In the OpenGL ES shading language. openGL ES 2.0 does not support the fixed function transformation and fragment pipeline of OpenGL ES 1. x.
OpenGL ES 2.0 currently does not support OpenGL es1.x. The concepts in OpenGL 2.0 are completely different from those in 1.x. It introduces shading and program objects, which makes programming quite troublesome.