some simple questions

I am a beginner for OpenGL. Could anyone
tell me:

  1. what is “GL_PROJECTION?”
  2. what is “GL_MODELVIEW?”
  3. what is “glOrhto?”
  4. and what is “glLoadIdentity()” for?

Thank you very much!

1 and 2
Matrix stacks in gl

3 sets up a frustum with orthographic view

that is a box in front of the screen instead of a truncated pyramid

loadidentity loads the identity matrix on the active matrix stack…

Look for the OpenGL red book.