_{This light can be used to simulate sunlight coming through a window}

This is a parallel light from a distant source, specified in terms of a direction vector. Often used to model sunlight.

The lights page has more detail about the controls.

Angle

The angular size of the light, in degrees. Non-zero values produce realistic soft shadows. For example, the Sun subtends approximately 0.5 degrees as seen from the surface of the Earth. A setting of 1 or 2 will produce slightly softened shadows like hazy sunshine, larger numbers such as six will be much softer. Note that increasing the angular area of the light will make it brighter, unless Normalize is on.