egles | Portable EGL layer , framework and wrappers for the Go | Game Engine library

The OpenGL, or OpenGL ES - is everything about rendering within some environment. It doesn't know or care about what exactly that environment is. As long as it provides required list of compliant functions that can be called to achieve desired result - that's OpenGL for you.

Now how do you create that environment? Since it's not OpenGL's responsibility, it has to be done by someone else, and it has to be done in a way that is compliant with rules of the system that hosts the rendering application.

That's where the EGL place is - it defines an API that gets translated to underlying windowing system calls by some library. Like GLX and WGL is responsible for creation of OpenGL context on Linux and Windows, EGL is responsible for creation of OpenGL ES context in embedded systems. Android is not the only platform that's using EGL, pretty much all the Linux-capable single-SoC ARM computers will expose EGL API, so apps would be able to create a valid rendering context.

If you never used EGL api - then it means you never wrote the native applications for Android, or some other java class (like GLSurfaceView) is wrapping up things for you. Look at the basic GLES examples, you'll find lots of references to EGL stuff. At the minimum you'd be asked to provide the EGLConfigChooser, or at least give some parameters to implicitly created EGLConfigChoser.