OpenGL ES Shading Language (ESSL) is the language in which we write our shaders. Its syntax and semantics are very similar to C/C++. However, it has types and built-in functions that make it easier and more intuitive to manipulate vectors and matrices. In this section, we will cover the basics of ESSL so we can start using it right away.
This section is a summary of the official GLSL ES specification. It is a subset of GLSL (the shading language for OpenGL).
You can find the complete reference at http://www.khronos.org/registry/gles/specs/2.0/GLSL_ES_Specification_1.0.17.pdf
Variable declarations may have a storage qualifier specified in front of the type: