For example, the light can reflect where dropped making it easy to position lights to reflect in the right place on your model.
The light is positioned in the right place in your 3D scene to create the desired lighting effect on your model. When using HDR Light Studio, the light is created and provided with this transparency image data, so that the area light does not have black borders. The light will usually have a shape such that outside this shape will need to be transparent. The texture is added to the area light and a HDRI link is established between the area light and HDR Light Studio.
The HDR Light Studio plug-in builds the area light for you in Cinema 4D
Once the light is dropped, here is what happens.