OpenGL ES 2.0 relies on a large collection of data and objects to render when you ask. You’ll need to compile and link shader programs, initialize vertex arrays and attribute bindings, specify uniform values, and probably load and bind texture, and that only scratches the surface.
There is also a large quantity of values that are intrinsic to OpenGL ES 2.0’s operation. You might need to determine how large of a viewport is supported, or the maximum number of texture units, for example. All of those values can be queried by your application.
This chapter describes the functions your applications can use to obtain values from OpenGL ES 2.0, and the parameters that you can query.