What is z-buffering?

I’m new to OpenGl, 3 days exactly. I know C++ though, but what i’m asking is what in the world is z-buffering?

its a depth test. It ensures that objects in your world are drawn in the right order.

ie, stuff at the back, isn’t drawn over whats in the front.

This means you do not have to sort for depth.
You can draw your objects in whatever order you like and the foremost should be visible anyway.
The z-buffer simply stores the depth value of each pixel and compares with this upon rendering.

so how do i code for this?

Well… are you using glut or win32 api?
You must first of all request a depthbuffer (z-buffer). In win32 api you set the cDepthBits members in the PIXELFORMATDESCRIPTOR structure to something like 16,24 or 32. I dont know exactly with glut but you should pass a GL_DEPTH_BUFFER or similar parameter when you initialize your window.
You must also enable depth testing with glEnable(GL_DEPTH_TEST) and you should set up an appropriate depthtest function with either glDepthFunc(GL_LESS) or glDepthFunc(GL_GREATER) depending on what fits your app.

Just a minor note to Humus post. In GLUT you pass GLUT_DEPTH to glutInitDisplayMode() to get a depthbuffer.

Thanks for the help, I was looking at NeHe’s tutorial and i believe he uses z-buffering so i get how to do it now.