What is the purpose of specifying a clear color in OpenGL ES?

Question

I'm working my way through the LibGDX framework, which provides a wrapper to make opengl calls. I regularly come across the following pair of functions:

Gdx.gl.glClearColor(0.0f, 0.0f, 0.0f, 1.0f); 
Gdx.gl.glClear(GL10.GL_COLOR_BUFFER_BIT); 

The documentation(from OpenGL) explains that glClearColor allows you to:

Specify the red, green, blue, and alpha values used when the color buffers are cleared.

What is the purpose of selecting a specific clear color here, when it is then immediately overwritten by whatever gets rendered? Should you choose a color that matches your scene? Is it used to set the background for the scene?

Answer 1

If you do actually overwrite every pixel in every frame you render, you don't need to clear the color buffer at all (but usually, you still have to clear the depth buffer).

However, there are lots of use cases where a cleared buffer is required, and being able to select the background color is a useful feature there.