_{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 6, will be much softer. Note that increasing the angular area of the light will make it brighter, unless Normalize is on.