The distance of the far clipping plane from the Camera, in world units.
The far clipping plane is furthest point of the Camera's view frustum. The Camera cannot see geometry that is further this distance. For more information, see Understanding the view frustum.
In the Unity Editor, this corresponds to the Clipping Planes: Far property in the Camera component Inspector.
Additional resources: Camera Inspector reference, Camera.nearClipPlane, layerCullDistances.