Unity Script Reference:
Legacy Documentation: Version 4.3.0
GL.Clear
static function Clear(clearDepth: bool, clearColor: bool, backgroundColor: Color, depth: float = 1.0f): void;
static void Clear(bool clearDepth, bool clearColor, Color backgroundColor, float depth = 1.0f);
static def Clear(clearDepth as bool, clearColor as bool, backgroundColor as Color, depth as float = 1.0f) as void
Parameters

clearDepth Should the depth buffer be cleared?
clearColor Should the color buffer be cleared?
backgroundColor The color to clear with, used only if clearColor is true.
depth The depth to clear Z buffer with, used only if clearDepth is true.
Description

Clear the current render buffer.

This clears the screen or the active RenderTexture you are drawing into. In most other situations, some camera is drawing something somewhere, and probably is clearing already with the background color of the skybox.

See Also: GL.ClearWithSkybox.