A point light source is defined by a center and a radius. A point light illuminates light to all directions. The radius attribute can be used for controlling the fall off.
It is also possible to set a 'size' attribute, in which case the point light becomes an area light generating soft shadows in a physically correct way.
Point light also supports an 'Ambient' option. If set, the light source no longer emits light rays radially but randomly to all directions. The position and size attributes are then used for controlling the strength of illumination. This allows the user to create local ambient lighting effects.
Point light specific options:
Point/Ambient light - The Ambient option turns the point light into an ambient light.
Position - The position of the light
Size - The radius of the light source. Size is used when computing mapped shadows. It is also used for ray traced smooth shadows i.e. when 'Quality' is greater than 0. The higher the size, the smoother the shadows become.
Quality - The sampling quality for ray traced smooth shadows. A high quality value increases rendering time but produces smooth shadows, whereas low values render quickly but may introduce some dithering artifacts at shadows edges. The bigger the light source size, the higher quality value is needed for a proper quality.