OpenGL ES is the mobile and lighter version of OpenGL, which is a powerful library of real-time 3D rendering. This is seen in a lot of newer phones and handhelds.
@orrymain: hmmmn... i am wondering which is not clear to you?
3D? Rendering? Real time?
it's really self explanatory if you take time to think about it? Please tell me where you're not clear and I'd explain it to you. Or better yet, go to wikipedia and look up each one... it might be a good learning experience....
if you can't find it on wiki... then maybe google is your friend :)