OpenGL is a state machine. 

• It has an inherent state represented by internal variables
• Variables initially are in their default state
• Variables changed through OpenGL calls

The advantage of this implementation is that fewer arguments are passed to OpenGL on each function call
 
A common source of programming errors results from the programmer misunderstanding or making incorrect assumptions about the OpenGL state
 
To enable a state variable, one can call

glEnable(GLenum capability);

To disable the capability, one calls

glDisable(GLenum capability);

One can test if a state variable is enabled with

glIsEnabled(GLenum capability);

High